Purification and Characterization of Cytosolic Serine Hydroxymethyltransferase from Euglena gracilis z.

Cytosolic serine hydroxymethyltransferase [L-serine: tetrahydrofolate 5, 10-hydroxymethyltransferase, EC 2.1.2.1] from Euglena gracilis z was purified by precipitation with ammonium sulfate followed by column chromatography on DEAE-cellulose, and by affinity chromatography on an L-adsorbent. Through this procedure the cytosolic enzyme (s-SHMT) was purified 420-fold with a yield of more than 26.8%. The preparation gave a single band with an Mr of 45, 000 on SDS-PAGE. The native enzyme contained 2 mol of pyridoxal phosphate/mol of enzyme, and had an Mr of 90, 000 on gel filtration, indicating a dimeric structure. Several other properties of the enzyme were also studied.