Purification of active recombinant serine racemase from mammalian
cells. Mouse serine racemase-GST fusion protein was expressed in HEK293
cells and purified to homogeneity. (A) SDS/PAGE
(12%) stained with Coomassie brilliant blue. Lane 1, 40 μg
transfected HEK293 cell protein extract; lane 2, 30 μg mouse serine
racemase-GST fusion protein purified with glutathione-Sepharose beads;
lane 3, 5 μg purified serine racemase after GST portion was removed
by cleavage with thrombin. (B) Serine racemase activity
was measured at 37°C in media containing 50 mM Tris⋅HCl (pH
8.2), 10 μg/ml recombinant serine racemase, 15 μM PLP, and
10 mM l-serine. Recombinant serine racemase exhibited
robust racemase activity (○), which was totally inhibited by
1 mM AOAA (●). The data are representative of six
different purifications.