THE UTILIZATION OF GLYCOLLATE BY MICROCOCCUS DENITRIFICANS: THE β-HYDROXYASPARTATE PATHWAY

Abstract

Micrococcus denitrificans utilized glycollate as sole C source for aerobic growth. Glyoxylate was not utilized as well, and though glycine alone did not support growth it enhanced growth on glyoxylate. During growth on glycollate, C14 was incorporated from [2-C14]glycollate into glycine and then into aspartate, malate and glutamate. No phosphoglycerate was labelled at first. Glyoxylate was the first product of glycollate utilization, and glycollate oxidase was inducilby formed on transfer of the organism to glycollate-containing media. Extracts of glycollate-grown M. denitrificans contained negligible glyoxylate-carboligase activity and only low tartronate semialdehyde-reductase activity. erythro-[beta]-Hydroxyaspartate is a key intermediate in glyoxylate utilization. Enzymes catalyzing the synthesis of erythro-[beta]-hydroxyaspartate from glyoxylate and glycine and the conversion of erythro-[beta]-hydroxyaspartate into oxaloacetate, were inducibly formed during growth on glycollate and on other substrates yielding glyoxylate. Methods for the assay of these enzymes were developed. The biosynthesis of cell materials from glycollate is accomplished by the "[beta]-hydroxyaspartate pathway" in M. denitrificans, a novel metabolic route that may also perform a catabolic role in glyoxylate oxidation.