Mammalian D‐Cysteine: A new addition to the growing family of biologically relevant D‐amino acids

Abstract Mammalian D‐Cysteine is racemized from L‐cysteine by serine racemase, a pyridoxal phosphate (PLP)‐dependent enzyme. 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 serine and cysteine, mammalian serine racemase may play important roles in neural development highlighting its importance in psychiatric disorders.