Preparation and assay of recombinant serine racemase

Serine racemase is a glial and neuronal enzyme that reversibly converts L-serine to D-serine, an endogenous co-agonist of N-methyl-D-aspartate receptor type glutamate receptors (NMDARs). Here we present methods to recombinantly express and purify serine racemase in bacteria and two complementary ways to determine D-serine levels in unknown samples. Furthermore, a detailed protocol of serine racemase activity assays is described that can be used to screen for activators and inhibitors in vitro.