Serine Racemase (SRR)

Sequence analysis predicted that the 340-amino acid protein, which is 88% identical to the mouse protein, contains a conserved pyridoxal 5-prime-phosphate (PLP)-binding region that includes a highly conserved lysine at position 56. Northern blot analysis revealed expression of a 2.7-kb SRR transcript, with highest levels in hippocampus and corpus callosum, intermediate levels in substantia nigra and caudate, and low levels in amygdala, thalamus, and subthalamic nuclei. Western blot analysis showed expression of a 37-kD protein, the same size as in mouse. Functional analysis showed that cells expressing SRR synthesized robust levels of D-serine but no other D-amino acid, and levels could be augmented by supplemental L-serine in the culture medium.