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







  • D-Serine: A Cross Species Review of Safety

AMeftah A, Hasegawa H, Kantrowitz JT. 
Front Psychiatry. 2021 Aug 10;12:726365. doi: 10.3389/fpsyt.2021.726365

This review focused on D-serine safety, physiology, dose-response and efficacy in clinical studies. Indeed, DAAO inhibitor safety was also discussed. In particular, D-serine doses >500 mg/kg were nephrotoxic in rats but not in mice and rabbits. Furthermore, D-serine may have a physiologic role in metabolic, extra-pyramidal, cardiac and other systems, but no other clinically significant safety concerns are revealed in the literature. In conclusion, D-serine appears safe at currently studied maximal doses, with potential safety in combination with DAAO inhibitors. MORE



  • An antibody-based enzymatic therapy for cancer treatment: The selective localization of D-amino acid oxidase to EDA fibronectin

Rosini E, Volpi NA, Ziffels B, Grimaldi A, Sacchi S, Neri D, Pollegioni L.
Nanomedicine. 2021 Aug;36:102424. doi: 10.1016/j.nano.2021.102424.

An antibody directed enzyme prodrug therapy based on administration of the ROS-generating enzyme D-amino acid oxidase (DAAO) and of D-amino acids was designed generating a chimeric protein by fusing the F8 antibody that recognizes the EDA of fibronectin (expressed on the tumor neovasculature) and an evolved DAAO variant (Q144R). The F8(scFv)-DAAO-Q144R recombinant protein was efficiently expressed in E. coli cells as fully soluble, active and stable protein that binds EDA and localizes in tumor tissues. The F8(scFv)-DAAO-Q144R conjugate generates a stronger cytotoxicity to tumor cells than the native enzyme, especially when an inhibitor of heme oxygenase-1 was used, making it a promising candidate for a selective antitumor oxidative therapy controlled by the substrate D-amino acid addition. MORE



  • Oral administration of D-serine prevents the onset and progression of colitis in mice

Asahara SI, Kido Y, Oshima S, Nagaishi T, Tsuchiya K, Ohira H, Okamoto R, Watanabe M.
J Gastroenterol. 2021 Aug;56(8):732-745. doi: 10.1007/s00535-021-01792-1.

Up to now, no report on potential interactions between D-amino acids and inflammatory bowel disease (IBD) was published. Here, mice treated with D-serine prior to the induction of colitis exhibited a reduction in T-cell infiltration into the lamina propria and colonic inflammation. Furthermore, D-serine suppressed the progression of chronic colitis when administered after the disease induction. Under in vitro conditions, D-serine suppressed the proliferation of activated CD4 T cells and limited their ability to differentiate to Th1 and Th17 cells. The authors propose that D-serine not only can prevent, but also has efficacious effects as a treatment for IBD. MORE





  • Antimicrobial effects of syndiotactic polypeptides

Hazam, P.K., Phukan, C., Akhil, R., Anjali Singh, Vibin Ramakrishnan 
Sci Rep 11, 1823 (2021).

In this paper syndiotactic polypeptides, i.e. polymers of alternating L- and D-amino acids with LDLD or DLDL backbone stereochemical sequence, were designed. These polypeptides can form stable gramicidin-like helical conformations. Some of them showed impressive antimicrobial activity against three difficult to treat bacterial species, and were equally potent in serum, at difference of polypeptides made of L-amino acids only. MORE





  • Enhancing Electrochemical Biosensor Selectivity with Engineered D-Amino Acid Oxidase Enzymes for D-Serine and D-Alanine Quantification

Siba Moussa, Giulia Murtas, Loredano Pollegioni, and Janine Mauzeroll
ACS Appl. Bio Mater. 2021, 4, 7, 5598–5604.

A methodology for developing D-amino acid oxidase (DAAO)-based biosensors with varying substrate selectivity was studied. The wild-type yeast DAAO and variants of human DAAO W209R and yeast M213G were characterized for their selectivity and activity on D-serine and D-alanine: following immobilization (for final biosensor design) the enzymes showed selectivity comparable to free DAAO. Notably, the use of a specific regeneration strategy allowed to improve the biosensor response. MORE





  • Bio-inspired poly-DL-serine materials resist the foreign-body response

Zhang, D., Chen, Q., Bi, Y., Haodong Zhang, Minzhang Chen, Jianglin Wan, Chao Shi, Wenjing Zhang, Junyu Zhang, Zhongqian Qiao, Jin Li, Shengfu Chen, Runhui Liu
Nat Commun 12, 5327 (2021).

This paper reports on the synthesis and use of a highly water soluble, biocompatible and easily accessible poly-D,L-serine (named PSer) material, with the aim to avoid implantation-caused foreign-body response (FBR). The PSer hydrogel caused negligible inflammatory response after subcutaneous implantation in mice for 1-2 weeks and no obvious collagen capsulation up to 7 months post-implantation. The PSer hydrogels showed low FBR, resembling the control group, and better compare with the widely used poly-ethyleneglycol hydrogel. MORE



  • D-Tyrosine enhancement of microbiocide mitigation of carbon steel corrosion by a sulfate reducing bacterium biofilm

Unsal, T., Wang, D., Kumseranee, S., Punpruk, S., Gu, T.
World journal of microbiology & biotechnology 2021 v.37 no.6 pp. 103

Microbiocides are used to control problematic microorganisms but high doses of microbiocides cause environmental and operational problems. Here, the biodegradable microbiocide 2,2-dibromo-3-nitrilopropionamide (DBNPA) has been used with D-tyrosine to treat microbial biofilms. Notably, 150 ppm DBNPA + 1 ppm D-tyrosine combination attained an 3-log reduction in sessile cell count and an additional 30% reduction in mass loss compared with 150 ppm DBNPA alone. MORE



  • Semi-rational design of L-amino acid deaminase for production of pyruvate and D-alanine by Escherichia coli whole-cell biocatalyst

Liu K, Yu H, Sun G, Liu Y, Li J, Du G, Lv X, Liu L. 
Amino Acids. 2021 Sep;53(9):1361-1371. doi: 10.1007/s00726-021-03067-8

In order to increase pyruvate (and D-alanine) production from D,L-alanine by a whole-cell Escherichia coli system expressing L-amino acid deaminase from Proteus mirabilis (PmiLAAD) a semi-rational design (by site-directed saturation mutagenesis) was carried out based on a novel high-throughput screening method for pyruvate. The V437I variant showed a catalytic efficiency 1.9-fold higher than the wild-type PmiLAAD. Indeed, the growth of the engineered strain BLK07 was increased by integrating the genes encoding for Xpk and Fbp (to construct non-oxidative glycolysis pathway): the, the N6-pm1-V437I gene was also integrated into the genome of BLK07. By this system, pyruvic acid titer reached 42.2 g/L with an L-alanine conversion of 77.6% and a D-alanine resolution of 82.4%. MORE



  • Protein Engineering of D-Succinylase from Cupriavidus sp. for D-Amino Acid Synthesis and the Structural Implications

Yosuke Sumida, Masayuki Yamasaki, Yoshiaki Nishiya, Shinya Kumagai, Toshihide Yamada, Masayuki Azuma
Advanced Synthesis and Catalysis, 19 August 2021.

D-Succinylase (DSA) from Cupriavidus sp. P4-10-C and N-succinyl amino acid racemase (NSAR) from Geobacillus stearothermophilus NCA1503 were used to produce D-amino acids via the dynamic kinetic resolution of N-succinyl-D,L-amino acids. To optimize this system, DSA variants with improved enantioselectivity were generated by directed evolution: the L182E one showed superior enantioselectivity and thermostability. The resolution of the crystal structure allowed to deep inside the enzyme’s properties. D-phenylalanine and D-tryptophan were produced in 90% conversion with about 99% ee by using coupled L182E DSA and NSAR in one-pot. MORE





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.



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