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The Editor’s pick selection of the most intriguing papers is highlighted in yellow.



  • Chiral Amino Acid Analysis in the Plasma of B6DAO-/- Mice Lacking D-Amino Acid Oxidase Activity

Chiharu ISHII, Takeyuki AKITA, Masashi MITA, Ryuichi KONNO, Kenji HAMASE 
Chromatography, 2023; 44 (1), pp. 39-43.


In this work a B6DAO-/- mouse strain lacking D-amino acid oxidase (DAAO) activity, and based on the genetic background of C57BL strain, was developed. The levels of D-alanine (Ala), D-aspartic acid (Asp), D-leucine (Leu), D-proline (Pro) and D-serine (Ser) were determined in the plasma of the control C57BL/6J and mutant B6DAO-/- mice by a two-dimensional LC-MS/MS system. The D-enantiomers of the neutral amino acids (Ala, Leu, Pro and Ser) significantly increased in the mutant B6DAO-/- mice (3.69-36.91 nmol/mL) compared to control mice (0.24-2.03 nmol/mL), whereas the amounts of D-Asp were similar.



  • Mammalian D-Cysteine: A new addition to the growing family of biologically relevant D-amino acids
    Roychaudhuri R 
    Chirality. 2023. doi: 10.1002/chir.23555. Online ahead of print.

Mammalian D-Cysteine is racemized from the L-enantiomer by the pyridoxal phosphate-dependent enzyme serine racemase. Endogenous D-cysteine plays a role in neural development by inhibiting proliferation of neural progenitor cells (NPCs) via protein kinase B (AKT) signaling mediated by the FoxO family of transcription factors. D-Cysteine binds to Myristoylated Alanine Rich C Kinase Substrate (MARCKS) and alters phosphorylation at Ser 159/163 and its translocation from the membrane. By racemizing both serine and cysteine, serine racemase may play important roles in neural development, as well as in psychiatric disorders. 





  • The D-amino acid oxidase inhibitor luvadaxistat improves mismatch negativity in patients with schizophrenia in a randomized trial
    O’Donnell P, Dong C, Murthy V, Asgharnejad M, Du X, Summerfelt A, Lu H, Xu L, Wendland JR, Dunayevich E, Buhl DL, Litman R, Hetrick WP, Hong LE, Rosen LB.
    Neuropsychopharmacology, 2023; 1-8. doi: 10.1038/s41386-023-01560-0

With the final aim to increase N-methyl-D-aspartate (NMDA) receptor function in schizophrenia, luvadaxistat, a D-amino acid oxidase (DAAO) inhibitor, has been evaluated. Here, a randomized, placebo-controlled, double-blind, two-period crossover phase 2a study assessing luvadaxistat 50 mg and 500 mg for 8 days in 31 patients with schizophrenia was performed. While no treatment effects of luvadaxistat at either dose in eyeblink conditioning was observed, a significant improvement in mismatch negativity and a statistical trend to improvement for auditory steady-state response at 40 Hz was apparent in both cases with 50 mg, but not with 500 mg, compared with placebo. It seems that luvadaxistat can improve an illness-related circuitry biomarker at doses associated with partial DAAO inhibition.



  • Blood levels of D-amino acids reflect the clinical course of COVID-19 Kimura-Ohba S, Takabatake Y, Takahashi A, Tanaka Y, Sakai S, Isaka Y, Kimura T Biochem Biophys Rep. 2023; 34:101452. doi: 10.1016/j.bbrep.2023.101452
D-Amino acids, rare enantiomers of amino acids, have been identified as biomarkers and therapeutic options for COVID-19. This work reports on the blood levels of various D-amino acids, including D-alanine, D-proline, D-serine, and D-asparagine in patients with severe COVID-19 requiring artificial ventilation, showing lower figures than the normal range. Notably, their increase preceded the recovery of respiratory function, as indicated by ventilation weaning, and was associated with the disappearance of the virus in the blood, but not with inflammatory manifestations or blood cytokine levels.



  • Structure-function insights into the role of D-amino acid oxidase mutations implicated in amyotrophic lateral sclerosis
    Khan, S., Gomes, J.
    Biophysical journal, 122(3S1) 2023

The D-amino acid oxidase (DAAO) protein metabolizes D-amino acids and maintains motoneuron function by regulating D-serine levels and N-methyl-D-aspartate-receptor activation in the brain and spinal cord. Mutations in DAAO are associated with Amyotrophic Lateral Sclerosis (ALS); the corresponding variant proteins were produced in E.coli (BL21) cells and characterized. The mutations affected the efficiency of the enzyme on D-Ser, altered the melting temperatures, and significantly hampered benzoate and FAD binding. The authors concluded that the reduced enzymatic activity may hinder the degradation of D-Ser which may accumulate and alter the homoeostasis of the motoneurons, consequently contributing to the pathogenic effect of the mutations.



  • D-Serine reduces the expression of the cytopathic genotoxin colibactin
    Hallam JC, Sandalli S, Floria I, Turner NCA, Tang-Fichaux M, Oswald E, O’Boyle N, Roe AJ
    Microb Cell. 2023 Mar 6;10(3):63-77. doi: 10.15698/mic2023.03.793

Escherichia coli strains harbour the pks island, a 54 kb genomic island encoding the biosynthesis genes for a genotoxic compound named colibactin, which induces DNA damage, cell cycle arrest and chromosomal instability in eukaryotic cells. Production of colibactin has been implicated in the development of colorectal cancer (CRC). This study reports about the inhibitory effect of D-serine on the expression of the pks island in both prototypic and clinically-associated colibactin-producing strains and determine the implications for cytopathic effects on host cells. D-Serine treatment reduced the cytopathic responses normally observed during infection of HeLa cells with pks+ strains and reduced the cellular senescence that was observable at 72 h post infection. The recent finding of an association between pks-carrying commensal E. coli and CRC, highlights the necessity for the development of colibactin targeting therapeutics, such as D-serine treatment.



  • D-Amino Acids and Cancer: Friends or Foes?
    Murtas G, Pollegioni L
    Int J Mol Sci. 2023; 24(4):3274. doi: 10.3390/ijms24043274

This review focuses on the effects of the D-amino acids on the growth and reproduction of cancerous cells. We reported on recent investigations showing altered D-amino acid levels in specific cancer types and on the various roles proposed for these biomolecules related to cancer cell proliferation, cell protection during therapy, and as putative, innovative biomarkers. We highlighted that few studies on human samples have been reported to date, suggesting a need for routine analysis of D-amino acid content and an evaluation of the enzymes involved in regulating their levels in clinical samples in the near future.



  • Cross-Protection against Acute Staphylococcus aureus Lung Infection in Mice by a D-Glutamate Auxotrophic Vaccine Candidate
    García P, Cabral MP, Beceiro A, Moscoso M, Bou G
    Vaccines (Basel). 2023;11(2):210. doi: 10.3390/vaccines11020210

Staphylococcus aureus is regarded as a threatening bacterial pathogen causing invasive pneumonia in healthcare settings and in the community: the set-up of an effective S. aureus vaccine is a priority. Starting from the vaccine candidate, 132 ΔmurI Δdat, which is auxotrophic for D-Glu and protects against sepsis caused by S. aureus, its potential to prevent staphylococcal pneumonia was investigated using an acute lung infection model in BALB/c mice. Intranasal inoculation of the vaccine strain yielded transitory colonization of the lung tissue, stimulated production of relevant serum IgG and secretory IgA antibodies in the lung and distal vaginal mucosa and conferred cross-protection to acute pneumonia caused by clinically important S. aureus strains.



  • Diagnosing Alzheimer’s Disease Specifically and Sensitively With pLG72 and Cystine/Glutamate Antiporter SLC7A11 AS Blood Biomarkers
    Lane, H.-Y., Lin, C.-H.
    The international journal of neuropsychopharmacology, 2023; 26(1), pp. 1–8

This study aimed to determine the accuracy of pLG72 protein (a D-amino acids oxidase modulator) in plasma and SLC7A11 (a cystine/glutamate antiporter) mRNA in white blood cells in diagnosing Alzheimer’s disease (AD), using 130 healthy controls and 109 unmatched AD patients. AD patients had markedly higher pLG72 levels and SLC7A11 mRNA ΔCT values than healthy controls, thus suggesting that pLG72 protein and SLC7A11 mRNA can distinguish AD patients from healthy controls with excellent specificity and sensitivity, respectively.



  • In Silico and In Vitro Screening of Serine Racemase Agonist and In Vivo Efficacy on Alzheimer’s Disease Drosophila melanogaster
    Lu, C.-H., Chang, H.-T., Hsu, L.-F., Ming-Hsueh Lee,Jack Cheng, Wu, D.C., Lin, W.-Y.
    Pharmaceuticals, 16(2), 280 2023

Modulating the D-serine level, the main co-agonist of the NMDA receptor, is a strategy to treat symptoms of the NMDA receptor hypofunction in Alzheimer’s disease. This investigation tried to identify serine racemase (SR) agonists, able to boost the conversion of L- to D-serine. The compound NSC294149 (2-amino-3-(3-nitroimidazo[1,2-a]pyridin-2-yl)sulfanylpropanoic acid) was identified as a potential SR agonist and confirmed its amelioration of the hazard ratio of survival of the AD model Drosophila melanogaster.



  • Determination of D-serine and D-alanine Tissue Levels in the Prefrontal Cortex and Hippocampus of Rats After a Single Dose of Sodium Benzoate, a D-Amino Acid Oxidase Inhibitor, with Potential Antipsychotic and Antidepressant Properties
    Huang CC, Wei IH, Yang HT, Lane HY
    Neurochem Res. 2023. doi: 10.1007/s11064-023-03884-1

The effects of the N-methyl-D-aspartate receptor activators D-serine, D-alanine, and sarcosine against schizophrenia and depression are promising. To avoid the use of high doses of D-Ser and sarcosine (associated with undesirable nephrotoxicity or worsened prostatic cancer) several DAAO inhibitors can be used. Here, the effects of the DAAO inhibitor sodium benzoate on the prefrontal cortex and hippocampal level of D-Ala (as well as on L-Ala, D,L-Ser, D,L-Glu, and glycine) was investigated. Sodium benzoate exerts antipsychotic and antidepressant-like effects without altering the D-Ser and D-Ala levels in the prefrontal cortex (PFC) and hippocampus. Anyway, sodium benzoate exhibited antipsychotic and antidepressant-like effects. Thus, the therapeutic effects of sodium benzoate seem independent of D-amino acids levels.



  • Environmental microplastics exposure decreases antioxidant ability, perturbs gut microbial homeostasis and metabolism in chicken
    Li A, Wang Y, Kulyar MF, Iqbal M, Lai R, Zhu H, Li K. 
    Sci Total Environ. 2023;856(Pt 1):159089. doi: 10.1016/j.scitotenv.2022.159089

The accumulation of microplastics (MPs) in organisms has led to their recognition as a major global ecological issue. The authors reported that MPs exposure decreased growth performance and antioxidant ability and impaired chickens’ intestine, liver, kidney, and spleen, coupled to a significant decrease in alpha diversity and alternations in taxonomic compositions. Metabolomics analysis indicated that 2561 (1190 up-regulated, 1371 down-regulated) differential metabolites were identified, mainly involved in 5 metabolic pathways, including D-amino acid metabolism, ABC transporters, vitamin digestion and absorption, mineral absorption, and histidine metabolism.



  • Analysis of Bacteriophage Behavior of a Human RNA Virus, SARS-CoV-2, through the Integrated Approach of Immunofluorescence Microscopy, Proteomics and D-Amino Acid Quantification
    Brogna C, Costanzo V, Brogna B, Bisaccia DR, Brogna G, Giuliano M, Montano L, Viduto V, Cristoni S, Fabrowski M, Piscopo M
    Int J Mol Sci. 2023; 24(4):3929. doi: 10.3390/ijms24043929

This paper investigates the initial behavior of a novel pathogen, SARS-CoV-2, on the human microbiome. Immunofluorescence microscopy combined with spectral counting performed at mass spectrometry of viral peptides in bacterial cultures, along with identification of D-amino acids within viral peptides in bacterial cultures and in patients’ blood was carried out. This approach establishes the possible expression or increase of viral RNA viruses in general (and SARS-CoV-2), and to determine whether or not the microbiome is involved in the pathogenetic mechanisms of the viruses. This knowledge is expected to open the way to possible future vaccines: the probiotics vaccine, engineered with the right resistance to viruses that attach to both the epithelium human surface and gut microbiome bacteria.



  • Characterization of a polyclonal antibody that is highly selective for the D-isoAsp-25 variant of mammalian histone H2B
    Aswad DW, O’Leary KS, Williams K
    Amino Acids. 2023; doi: 10.1007/s00726-023-03242-z

Approximately 12% of histone H2B molecules in mammalian brain contain a modification wherein Asp25 is present as the D-enantiomer, and is mostly linked to Gly26 via the side-chain carboxyl. These authors reported about the high specificity of a polyclonal antibody to this modification, and its use to demonstrate that this modification is enriched in brain relative to liver, thymus, and HeLa cells.





  • RNA sequencing data analysis of the yeast Vanrija (Cryptococcus) humicola strain UJ1 grown on L- and D-aspartate
    Imanishi D, Takahashi S
    Data Brief. 2023; 47:109008. doi: 10.1016/j.dib.2023.109008

The yeast Vanrija (previously Cryptococcus) humicola strain UJ1 produces D-aspartate oxidase (DDO or DASPO) only in the presence of D-aspartate in culture media. This article provides RNA-sequencing data to identify the differentially expressed genes (DEGs) in the yeast cells grown on L- or D-aspartate. The DEGs were subjected to gene ontology and KEGG pathway enrichment analyses, to provide data on the possible biological functions of the DEGs.



  • Biodegrading plastics with a synthetic non-biodegradable enzyme Guo, C., Zhang, L.-Q., Jiang, W. Chem, 9(2), pp. 363–376 2023
Biodegradation of plastics through the use of enzymes is a useful and environmentally friendly solution to dispose and recycle plastic wastes. Plastics such as polyethylene terephthalate (PET), are achiral and thus should be hydrolyzed by both the L- and D-amino acid versions of plastic-degrading enzymes. Here, a mirror-image version of the 231-aa long PET hydrolase we chemically synthesized, which is capable of efficiently degrading a variety of plastics such as PET, polybutylene terephthalate, and polybutylene succinate. The synthetic mirror-image PET hydrolase demonstrates the potential of a new class of plastic-degrading, non-biodegradable mirror-image enzymes.



  • Promising applications of D-amino acids in periprosthetic joint infection

Caldwell M, Hughes M, Wei F, Ngo C, Pascua R, Pugazhendhi AS, Coathup MJ
Bone Res. 2023; 11(1):14. doi: 10.1038/s41413-023-00254-z

Periprosthetic joint infection (PJI) represents one of the most challenging complications that can occur following total joint arthroplasty (TJA), and as the number of primary and revision TJAs continues to rise, an increasing PJI burden is projected. Despite advances in operating room sterility, antiseptic protocols, and surgical techniques, approaches to prevent and treat PJI remain difficult, primarily due to the formation of microbial biofilms. D-amino acids are known to regulate cell morphology, spore germination, and bacterial survival, evasion, subversion, and adhesion in the host immune system. When administered exogenously, accumulating data have demonstrated that D-AAs play a pivotal role against bacterial adhesion to abiotic surfaces and subsequent biofilm formation; furthermore, D-AAs have substantial efficacy in promoting biofilm disassembly. This review examines the role of D-AAs in the context of TJAs.



  • Chiral polypeptide nanoparticles as nanoadjuvants of nanovaccines for efficient cancer prevention and therapy
    Su Y, Xu W, Wei Q, Ma Y, Ding J, Chen X
    Sci Bull (Beijing). 2023; 68(3):284-294. doi: 10.1016/j.scib.2023.01.024

In this work, two chiral polypeptides, namely poly(L-phenylalanine)-block-poly(L-lysine) (PL-K) and poly(L-phenylalanine)-block-poly(D-lysine) (PD-K), were synthesized and used as nanoadjuvants of nanovaccines for cancer prevention and therapy. The amphiphilic polypeptides self-assembled into nanoparticles (diameter = 30 nm) during ultrasonic-assisted dissolution in phosphate-buffered saline. The nanovaccines PL-K-OVA and PD-K-OVA were easily prepared by mixing solutions of PL-K or PD-K and the model antigen chicken ovalbumin (OVA), respectively, with full loading efficiencies. Compared to PL-K-OVA, PD-K-OVA more robustly induced dendritic cell maturation, antigen cross-presentation, and adaptive immune response; it also effectively prevented and treated the OVA-expressed B16-OVA melanoma model. PD-K-OVA achieved a tumor inhibition rate of >94% and even 97% by combining with anti-PD-1 antibody.



  • Photoinduced Processes in Lysine-Tryptophan-Lysine Tripeptide with L and D Tryptophan
    Ageeva AA, Lukyanov RS, Martyanova SO, Magin IM, Kruppa AI, Polyakov NE, Plyusnin VF, Doktorov AB, Leshina TV
    Int J Mol Sci. 2023; 24(4):3331. doi: 10.3390/ijms24043331

Optical isomers of short peptide Lysine-Tryptophan-Lysine (Lys-{L/D-Trp}-Lys) and Lys-Trp-Lys with an acetate counter-ion were used to study photoinduced intramolecular and intermolecular processes of interest in photobiology. Using NMR, chemically induced dynamic nuclear polarization (CIDNP) and fluorescence techniques, the influence of tryptophan (Trp) optical configuration on the peptides fluorescence quantum yields, bimolecular quenching rates of Trp excited state, and the photocleavage products formation, was investigated. Thus, compared with the D-, the L-isomer shows a greater Trp excited state quenching efficiency with the electron transfer (ET) mechanism.



  • Activation of D-Asparagine and D-Glutamine Derivatives Using the Mitsunobu Reaction
    Fu X, Shang Y, Chen S, Dedkova LM, Hecht SM
    Org Lett. 2023; 25(8):1310-1314. doi: 10.1021/acs.orglett.3c00232

Seven D-amino acid derivatives having reactive side chains have been activated to afford their respective 3,5-dinitrobenzyl esters using the Mitsunobu reaction. In detail, the conversion of a tRNA to the respective D-glutaminyl-tRNA using D-Gln 3,5-dinitrobenzyl ester was catalyzed by a flexizyme, followed by purification to remove all the unacylated tRNAs and other byproducts. Both D- and L-Gln were incorporated from their aminoacyl-tRNAs into a model peptide structurally related to IFN-β.



  • D-amino acid auxotrophic Escherichia coli strain for in vivo functional cloning of novel D-amino acid synthetic enzyme Ito T, Muto N, Sakagami H, Tanaka M, Hemmi H, Yoshimura T FEBS J. 2023; doi: 10.1111/febs.16734
In order to identify D-amino acid biosynthetic enzymes, here the first organism that exhibits non-canonical D-amino acid auxotrophy was set up. An Escherichia coli strain lacking the major D-Ala and D-Glu biosynthetic enzymes, alr, dadX, and murI, and expressing the mutated D-amino acid transaminase (DAAT) gene from Bacillus sp. YM-1 (MB3000/mdaat+) grew well when supplemented with selected D-amino acids. A multicopy suppression study with plasmids encoding one of the 51 PLP-dependent enzymes of E. coli showed that MB3000/mdaat+ could detect weak and moonlighting racemase activity. This platform will contribute to further research in this field by identifying novel D-amino acid-metabolizing enzymes.



  • Enhancement in the catalytic efficiency of D-amino acid oxidase from Glutamicibacter protophormiae by multiple amino acid substitutions
    Xu S, Chu M, Zhang F, Zhao J, Zhang J, Cao Y, He G, Israr M, Zhao B, Ju J
    Enzyme Microb Technol. 2023; 166:110224. doi: 10.1016/j.enzmictec.2023.110224

Sequence alignment of D-amino acid oxidase (DAAO) from Glutamicibacter protophormiae (GpDAAO-1) and (GpDAAO-2), identified 4 residues (E115, N119, T256, T286) at the surface regions of GpDAAO-2: their mutagenesis generated 4 single-point variants with enhanced catalytic efficiency. Here, a total of 11 (6 double, 4 triple, and 1 quadruple-point) variants were prepared by combinations of 4 starting single-point ones. The triple-point E115A/N119D/T286A enzyme exhibited the most significant improvement in catalytic efficiency; structural modeling analysis was used to rationalize the observed changes.



  • Bioinformatics-Structural Approach to the Search for New D-Amino Acid Oxidases Atroshenko DL, Golovina DI, Sergeev EP, Shelomov MD, Elcheninov AG, Kublanov IV, Chubar TA, Pometun AA, Savin SS, Tishkov VI Acta Naturae. 2022; 14(4):57-68. doi: 10.32607/actanaturae.11812
D-amino acid oxidases (DAAO) from different sources show very low homology between amino acid sequences, especially in bacteria. Here, an approach that uses bioinformatic methods in combination with general 3D structure and active center structure analysis was used to confirm that the gene found encodes DAAO and to predict about its substrate specificity. The effectiveness of the proposed approach for discrimination of DAAOs and glycine oxidases is also reported. Using this approach, new DAAO genes were found in the genomes of six strains of extremophilic bacteria, and for the first time in the world, one gene was identified in the genome of halophilic archaea (Natronosporangium hydrolyticum ACPA39) which is active on D-Leu and D-Phe.



  • Structure of pyridoxal 5′-phosphate-bound D-threonine aldolase from Chlamydomonas reinhardtii
    Hirato Y, Goto M, Mizobuchi T, Muramatsu H, Tanigawa M, Nishimura K
    Acta Crystallogr F Struct Biol Commun. 2023; 79(Pt 2):31-37. doi: 10.1107/S2053230X23000304

D-Threonine aldolase (DTA), a pyridoxal-5′-phosphate-dependent enzyme, catalyzes the reversible aldol reaction of glycine with a corresponding aldehyde to yield the D-form β-hydroxy-α-amino acid. Here, the crystal structure of DTA from Chlamydomonas reinhardtii (CrDTA) at 1.85 Å resolution was reported. Compared with the structure of bacterial DTA, some non-conserved residues could alter the affinity for substrates and inhibitors.



  • To the Understanding of Catalysis by D-Amino Acid Transaminases: A Case Study of the Enzyme from Aminobacterium colombiense
    Shilova SA, Khrenova MG, Matyuta IO, Nikolaeva AY, Rakitina TV, Klyachko NL, Minyaev ME, Boyko KM, Popov VO, Bezsudnova EY
    Molecules. 2023; 28(5):2109. doi: 10.3390/molecules28052109

Pyridoxal-5′-phosphate (PLP)-dependent transaminases are highly efficient biocatalysts for stereoselective amination and the D-amino acid transaminases (DAAT) can catalyze stereoselective transamination producing optically pure D-amino acids. Here, the authors report on DAAT from the Gram-negative bacterium Aminobacterium colombiense with a substrate binding mode different from that for the transaminase from B. subtilis. Notably, the substrate can act as a base and its proton can be transferred from the amino group to the α-carboxylate group. This process occurs simultaneously with the nucleophilic attack of the PLP carbon atom by the nitrogen atom of the substrate forming gem-diamine at the transimination step. This observation explains the absence of the activity toward (R)-amines that lack an α-carboxylate group.



  • Co-Immobilization of D-Amino Acid Oxidase, Catalase, and Transketolase for One-Pot, Two-Step Synthesis of L-Erythrulose
    Świętochowska, D., Łochowicz, A., Ocal, N., Pollegioni, L., Charmantray, F., Hecquet, L., Szymańska, K. 
    Catalysts 2023; 13, 95.

This work report on the immobilized enzyme cascade in a basket-type reactor allowing a one-pot, two-step enzymatic synthesis of L-erythrulose from D-serine and glycolaldehyde. D-amino acid oxidase from Rhodotorula gracilis (DAAORg), catalase from bovine liver (CAT), and transketolase from Geobacillus stearothermophilus (TKgst) were covalently immobilized on silica monolithic pellets. The best L-erythrulose production was obtained for the co-immobilization protocols using two of the three enzymes followed by the third and co-immobilization of all three enzymes.





  • Endogenous L- to D-amino acid residue isomerization modulates selectivity between distinct neuropeptide receptor family members
    Yussif BM, Blasing CV, Checco JW
    Proc Natl Acad Sci U S A. 2023; 14;120(11):e2217604120. doi: 10.1073/pnas.2217604120

The isomerization of amino acid residues of neuropeptides is an understudied post-translational modification found in animals across several phyla. Here, the Checco’s group demonstrated that the Aplysia allatotropin-related peptide (ATRP) signaling system utilizes L- to D-residue isomerization of one amino acid residue in the neuropeptide ligand to modulate selectivity between two distinct G protein-coupled receptors (GPCRs). The authors identified a novel receptor for ATRP that is selective for the D2-ATRP form, which bears a single D-Phe residue at position 2; then the ATRP system was demonstrated to display dual signaling through both the Gαq and Gαs pathways, and each receptor was selectively activated by one naturally occurring ligand diastereomer over the other.



  • Teicoplanin aglycone media and carboxypeptidase Y: Tools for finding low-abundance D-amino acids and epimeric peptides
    Sung YS, Khvalbota L, Dhaubhadel U, Špánik I, Armstrong DW
    Chirality. 2023. doi: 10.1002/chir.23543. Online ahead of print.

D-amino acids and epimeric peptides/proteins can play crucial biological roles and adversely affect protein folding and oligopeptide aggregation in age-related pathologies in humans. This work evaluated the use of teicoplanin aglycone, a macrocyclic antibiotic as a solid phase extraction (SPE) medium. Retention curve differences between amino acids and peptides highlighted regions of solvent composition that can be utilized for their separation. This approach is especially useful when coupled with enzymatic hydrolysis by carboxypeptidase Y to eliminate all L-amino acid exclusive peptides.



  • D-amino acid peptides as antimicrobial agents against vibrio-associated diseases in aquaculture
    Monserrat López-Sanmartín, Rocío Rengel, Manuel López-López, José A. Lebrón, Ana Molina-Márquez, Ignacio de la Rosa, Pilar López-Cornejo, Alberto Cuesta, Javier Vigara, Rosa León
    Aquaculture, 569, 739362 2023,

Vibriosis is a usual infection disease in bivalve mollusks. Antimicrobial peptides (AMPs) are a promising alternative, however, their low stability can represent a significant drawback. Here, the structure and stability of a synthetic all-D-amino acid peptide (D-Caerin) to proteases and extreme pH conditions have been analysed in comparison with its corresponding natural L-enantiomer peptide, Caerin 1.1. Moreover, the antimicrobial activity of D-Caerin has been tested in vitro against the control bacteria Micrococcus luteus CECT 245 and four Vibrio species representative causative agents of vibriosis in aquaculture. The results demonstrate that D-Caerin contains two left-handed alpha helices, and is more stable and effective against the bacterial species tested than its L- counterpart. The bioactivity of D-Caerin has also been tested in vivo: D-Caerin-treated specimens exhibited higher survival rates after infection.



  • Combination D-Amino Acid and Photothermal Hydrogel for the Treatment of Prosthetic Joint Infections
    Milbrandt NB, Tsai YH, Cui K, Ngompe Massado CS, Jung H, Visperas A, Klika A, Piuzzi N, Higuera-Rueda CA, Samia ACS
    ACS Appl Bio Mater. 2023; 6(3):1231-1241. doi: 10.1021/acsabm.2c01083.

Prosthetic joint infection (PJI) is a devastating complication that involves the formation of bacterial biofilms. Here, a combination treatment that is based on a hydrogel nanocomposite system, containing D-amino acids (D-AAs) and gold nanorods has been developed. Using this two-step approach to utilize a near-infrared light-activated hydrogel nanocomposite system for thermal treatment, following initial disruption with D-AAs, the total eradication of Staphylococcus aureus biofilms grown on three-dimensional printed Ti-6Al-4V alloy implants was demonstrated. On the other hand, only 25% eradication of the biofilms was apparent using the debridement, antibiotics, and implant retention method.



  • Characterization of Bacillus tequilensis A1C1: A Novel Bio-reservoir of D-serine
    Kapil, S., Sharma, V., Kumar, T.
    Research Journal of Biotechnology, 2023; 18(2), pp. 8–14.

The strain Bacillus tequilensis was identified from bacteria isolated from the pomace dumping soil site that showed maximum growth within 48h in the minimal salt media supplemented with L-serine. The D-serine concentration was 0.92 nM in the cellular fraction. Furthermore, the Bacillus tequilensis A1C1 has antibacterial activity against MTCC 40 and MTCC 11949.

  • Development of a Versatile Method to Construct Direct Electron Transfer-Type Enzyme Complexes Employing SpyCatcher/SpyTag System
    Yanase, T., Okuda-Shimazaki, J., Asano, R., Kazunori Ikebukuro, Sode, K., Tsugawa, W.
    International Journal of Molecular Sciences, 2023; 24(3), 1837.

This work focused on the development of a versatile approach to create a direct electron transfer (DET)-type oxidoreductase complex based on the SpyCatcher/SpyTag technique by preparing SpyCatcher-fused heme c and SpyTag-fused non-DET-type oxidoreductases, and by the in vitro formation of DET-type oxidoreductase complexes. A heme c containing an electron transfer protein derived from Rhizobium radiobacter (CYTc) was selected, as well as three non-DET-type oxidoreductases (fungal glucose dehydrogenase, an engineered D-amino acid oxidase, and an engineered L-lactate oxidase. CYTc-SpyCatcher and SpyTag-Enzymes were prepared as soluble molecules while maintaining their redox properties and catalytic activities, respectively. CYTc-SC/ST-Enzyme complexes were formed by mixing CYTc-SpyCatcher and SpyTag-Enzymes: the heme domain served as an electron acceptor from complexed enzymes by intramolecular electron transfer: all the CYTc-SC/ST-Enzyme complexes showed DET ability to the electrode.



  • Progress in Research on the Formation Mechanism and Physiological Functions of D-Amino Acids in Foods
    Gao, L., Xu, P., Ren, J.
    Shipin Kexue/Food Science, 2023; 44(1), pp. 256–267.

Daily diet is an important source of D-amino acids for humans, with an average supply for humans of about 100 mg/day. This review reports D-amino acids in foods (origin, functions, etc).





  • Enantiomeric purity analysis of synthetic peptide therapeutics by direct chiral high-performance liquid chromatography-electrospray ionization tandem mass spectrometry
    Strege, M.A., Oman, T.J., Risley, D.S., Laura K Muehlbauer , Jalan, A., Jerry Lian, Z.
    Journal Chromatography B: Analytical Technologies in the Biomedical and Life Sciences, 2023; 1219, 123638

The determination of chiral purity is critical to the evaluation of the quality of peptide pharmaceutical products. A chiral high-performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) method is described here to facilitate rapid and accurate determination of amino acid chiral purity of a peptide. The peptide is hydrolyzed in deuterated acid to facilitate correction for any racemization occurring during this step of sample preparation, and the amino acids are subsequently separated by chiral chromatography interfaced with ESI-MS/MS for quantitation. The amino acid samples are analyzed directly following hydrolysis using high-low chromatography and extraction of selected ion response, providing efficiency and simplicity by avoiding the derivatization. GMP method validation feasibility is described for all nineteen chiral proteogenic amino acids. The practical application was demonstrated through the recovery of D-amino acid substitutions at each residue of an octapeptide across the 0.1-1.0% range of interest. 



  • Determination of D- and L-Amino Acids in Garlic Foodstuffs by Liquid Chromatography-Tandem Mass Spectrometry
    Onozato M, Nakanoue H, Sakamoto T, Umino M, Fukushima T
    Molecules. 2023; 28(4):1773. doi: 10.3390/molecules28041773

Here, the D- and L-amino acid compositions of methanol extracts from fresh and black garlic were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) using a pre-column chiral derivatization reagent, succinimidyl 2-(3-((benzyloxy)carbonyl)-1-methyl-5-oxoimidazolidin-4-yl) acetate. The results demonstrated that several D-amino acids can be produced during fermentation for preparing black garlic.



  • Characterization of low-level D-amino acid isomeric impurities of Semaglutide using liquid chromatography-high resolution tandem mass spectrometry
    Zhang, B., Xu, W., Yin, C., Tang, Y.
    Journal of Pharmaceutical and Biomedical Analysis, 2023; 224, 115164

Since trace amount of impurity may influence the efficacy and safety of the pharmaceuticals, the characterization and quantification of peptide impurities is a crucial task in pharmaceutical development, Biological Semaglutide, a glucagon-like peptide-1 (GLP-1) agonist approved for the treatment of type II diabetes mellitus and weight control can be substituted by a synthetic one. In this work, by reverse-phase high-performance liquid chromatography (RP-HPLC) and tandem mass spectrometry, the levels of D-Ser, D-His and D-Asp Semaglutide degradants have been evaluated.



  • Simultaneous quantification of five DL-amino acids in beer by UHPLC–MS/MS using a novel chiral mass spectrometry probe
    Yan Zhu, Lei Di,  Shengyu Cheng, Yueying Jin, Minghui Zhang, Lingli Zhang, Xin Wang, Xi-Ling Li, Yu Han,  Chun-Yan Xum Jun Zhe Min 
    Eur Food Res Technol 2023; 249, 1137–1146.

A novel UHPLC–MS/MS method with high sensitivity and selectivity for simultaneous detection and chiral resolution of D,L-amino acids in beer was established using the mass spectrometry probe (S)-(3-(4-carboxythiazolidin-3-yl)-3-oxopropyl) diphenylsulfonium. The resolutions of D,L-amino acids ranged from 1.71 to 5.42; the correlation coefficients were ≥ 0.9994 in the range of 0.25 to 1200 pmol, the limits of detection (LOD) and limits of quantitative (LOQ) analysis were 0.05–0.25 pmol and 0.13–0.50 pmol, respectively. The results showed that D-amino acids are abundant in beer, especially D-Ala, D-Pro, D-Glu, D-Phe (1.9–29.8 μmol L−1), as well as five L-AAs (L-Pro, L-Ala, L-Phe, L-Glu, L-Asp; 5.3–2315.9 μmol L−1).



  The D-amino acids International Research Center “DAAIR“ has been established in Gerenzano (Varese, Italy) in 2019 with the aim to support and perform scientific research projects and activities on the field of D-amino acids. The Center, located inside the Fondazione Istituto Insubrico Ricerca per la Vita, is aimed to represent a pole of excellence at international level for dissemination and research involving the D-amino acids (Director Silvia Sacchi).   The guiding principle is support the research projects aimed to investigate the involvement of D-amino acids in main physiological processes, from bacteria to humans. The ultimate goal is to actively participate to the elucidation of the mechanisms by which the D-amino acids perform specific functions, and to identify their presence and concentration in different organisms and compartments, also with regards to well-established functional states, with particular emphasis to pathological states. Understand the involvement of D-amino acids in important diseases as a way to set up novel therapeutic strategies.   Contacts:;;   
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