Glycine Synthesis and Metabolism in Escherichia coli

Abstract

A correlation was demonstrated between a nutritional requirement that can only be satisfied by glycine and the absence of the enzymatic capacity to interconvert L-serine and glycine. Serine synethesis from 3-phosphoglycerate was observed in the same cell-free extracts which could not convert serine to glycine. The above results show that serine is the precursor or glycine under normal growth conditions. The C-2 of glycine provided "one-carbon** fragments when the C-3 of serine was not available as the source of "one-carbon" fragments. This condition occurred when a mutation produced a loss of serine aldolase activity or when a serine-glycine auxotroph was grown with glycine. Under these growth conditions, 30 to 40% of the "one-carbon" fragments used for cellular synthesis were derived from glycine.