Advances in D-amino Acids Research: New Insight in Physiology, Metabolism and Applications

Dear Colleagues,

All amino acids other than glycine exist in either the L- and D-enantiomers, which are mirror images of each other. D-amino acids (D-AAs) were long considered to be “the wrong isoform”, i.e., they were taken to be non-functional or even absent in living organisms, with the exception of bacteria. Over the last few decades, however, they were found to be widely distributed in plants, invertebrates, and vertebrates including humans, and have since been acknowledged to play a role in several key biological processes. Moreover, accumulated evidence of their physiological functions and metabolic pathways (biosynthesis, transport and degradation) has led to a keen, renewed interest in their study.

D-AAs are fundamental in microbial physiology as key constituents of the peptidoglycan layer. They are also produced and released by several bacterial species and act as effector molecules, regulating cell wall biogenesis, biofilm integrity, and spore germination. In mammals, D-serine, D-aspartate, and D-alanine represent the most abundant D-AAs in neuroendocrine and endocrine tissues and, due to their contribution to neurotransmission, the most studied ones. These and others D-AAs have also been implicated in regulating innate immunity and gut barrier function. Worthy of note, increasing evidence supports a role for D-AAs in pathological processes, including neurological diseases, psychiatric disorders, chronic kidney disease and cancer. Moreover, the scientific community has begun to recognize the potential of D-AAs as biomarkers, but also as therapeutic agents for treating neurological diseases and tissue/organ injury, ameliorating reproduction function, and preventing biofilm infection.

The aim of this Special Issue is to catalyze the interest of people working in the field and publish their recent research. Potential topics include recent research into D-AAs, their biological roles in different organisms, their metabolism, their involvement in pathologies, and their use as biomarkers for diagnostic purposes and add-on therapies to pharmacological treatments. Overall, our objective is to further broaden the horizons of this research topic, which no longer represents a niche.

Dr. Silvia Sacchi
Dr. Jumpei Sasabe
Guest Editors

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• metabolism
• microbiota
• cell signaling
• neuromodulators
• endocrine modulators
• pathological processes
• diagnosis
• biomarker
• peptidoglycan
• biofilms