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

Abstract

1. Micrococcus denitrificans utilized glycollate as sole carbon source for aerobic growth. Glyoxylate was utilized less well, and though glycine alone did not support growth it enhanced growth on glyoxylate. 2. During growth on glycollate, (14)C was incorporated from [2-(14)C]glycollate into glycine and thence into aspartate, malate and glutamate. No phosphoglycerate was labelled at the earliest times. 3. Glyoxylate was the first product of glycollate utilization, and glycollate oxidase was inducibly formed on transfer of the organism to glycollate-containing media. 4. Extracts of glycollate-grown M. denitrificans contained negligible glyoxylate-carboligase activity and only low tartronate semialdehyde-reductase activity. 5. erythro-beta-Hydroxyaspartate is a key intermediate in glyoxylate utilization by this organism. Enzymes catalysing (a) the synthesis of erythro-beta-hydroxyaspartate from glyoxylate and glycine, and (b) 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. 6. It is concluded that in M. denitrificans the biosynthesis of cell materials from glycollate is accomplished by the ;beta-hydroxyaspartate pathway', a novel metabolic route that may also perform a catabolic role in glyoxylate oxidation.