BackgroundD-Serine. an endogenous co-agonist of the N-methyl-D-aspartate (NMDA) receptor. is synthesized from L-serine by serine racemase (SRR). Given the role of D-serine in both neurodevelopment and the pathophysiology of schizophrenia. https://www.herbsdailyes.shop/product-category/l-tryptophan/