Primary structure studies on serine hydroxymethyltransferase

Serine hydroxymethyltransferase (EC 2.1.2.1) is a pyridoxal-phosphate containing enzyme which, among other reactions, catalyzes the tetrahydrofolate-dependent interconversion of serine and glycine, thus representing the major source of one-carbon groups required for the biosynthesis of several cell components. Both cytosolic and mitochondrial forms exist in eukaryotic cells and preliminary sequence studies have demonstrated that these two isoenzymes are homologous proteins. Recemtly, the nucleotide sequence of the Escherichia coli GlyA gene has been determined and the deduced protein sequence was supposed to be that of serine hydroxymethyltransfease. Comparison of the structure of the available peptides from the cytosolic enzyme with the sequence of the putative enzyme from E. coli, confirmed the identification of the latter and was useful in reconstructing the sequence of the former.