Eukaryotic d-Serine Dehydratase

Abstract

In mammals, d-serine is endogenously synthesized by serine racemase (SR), and it plays important roles in memory and learning by binding to the N-methyl-d-aspartate (NMDA) receptor and δ2 glutamate receptor. d-Amino acid oxidase (DAO) is the only mammalian enzyme that degrades d-serine. Many eukaryotes, excluding mammals, have another d-serine-degrading enzyme, d-serine dehydratase (DSD). DSD is a pyridoxal 5′-phosphate (PLP)- and Zn2+-dependent enzyme that catalyzes the deamination of d-serine to produce pyruvate and ammonia, and it is distinct from the classical d-serine dehydratases such as DsdA of Escherichia coli. In chicken, DSD is expressed in the kidney, liver, and brain, and it plays a primary role in removing d-serine from the circulating blood. The cellular slime mold Dictyostelium discoideum contains three d-serine-metabolizing enzymes, SR, DAO, and DSD. Among these enzymes, DSD is responsible for d-serine degradation. Although the physiological significance of DSD is still unclear, it is thought to contribute to the maintenance of d-serine at low levels in these organisms. This article describes the biological distribution, physiological role, enzyme properties, structure, reaction mechanism, and application of DSD based on recent studies of the enzyme in chicken and yeast.