Serine racemase（SRR) is an enzyme which generates D-serine from L-serine. D-serine functions as a neuronal signaling molecule by activating NMDA receptors in the brain. Mammalian SRR is a pyridoxal 5’-phosphate dependent enzyme which catalyzes both the racemization of L-serine to D-serine and also the elimination of water from L-serine， producing pyruvate and ammonia. The SRR enzyme is physiologically stimulated by divalent cations（e.g.， magnesium) and is allosterically activated by the magnesium/ATP complex.
