Affinity purification and characterization of serine hydroxymethyltransferases from rat liver.

A rapid and simple method was developed for the purification of serine hydroxymethyltransferases [EC 2.1.2.1]. The procedure involved ammonium sulfate precipitation, DEAE-cellulose column chromatography and affinity chromatography on an L-adsorbent. Through this procedure the cytosolic enzyme (s-SHMT) was purified 1,650-fold, and the mitochondrial enzyme (m-SHMT) 1,730-fold, with a yield of more than 30% in both cases. Both preparations gave a single band with a Mr of 54,000 on SDS-PAGE. The native enzymes both contained 4 mol of pyridoxal phosphate/mol of enzyme, and showed a Mr value of 220,000 on gel filtration, indicating a tetrameric structure. Several other properties of the enzymes were also studied.