Synthesis of cell constituents from glycine by a Pseudomonas

Abstract

When Pseudo-monas (A) grown with glycine as sole C source was harvested after 20 hr. in the stationary phase and suspended in fresh medium, cell division was delayed for 4 hr. and pyruvate accumulated. Fluoro-acetate and arsenite inhibited oxidation of glycine by these cells. They contained no serine dehydrase. Extracts of cells grown with glycine catalyzed the evolution of one molecule of CO2 from two molecules of glyoxylate. This enzyme (glyoxylate carboligase) required thiamine pyrophosphate and magnesium ions for maximal activity. The product, presumed to be tartronic semialdehyde, decomposed spontaneously at pH 7.2 at the rate of 50% in 50 min. to give glycolaldehyde. The bis-2,4-dinitrophenylhydrazone of tartronic semialdehyde was separated from that of glycolaldehyde (glyoxal) by reverse-phase chromatography, and its absorption spectrum in alkali obtained. Cell extracts contained an enzyme (tartronic semialdehyde reductase) that catalyzed reduction of tartronic semialdehyde to glycerate. When coupled with glyoxylate carboligase, one molecule of glycerate was formed from two molecules of glyoxylate, and one molecule of DPNH was oxidized. Cell extracts converted glycerate into pyruvate, phosphate esters of glyceric acid being formed as reaction intermediates. Malate synthetase was present in extracts. From these results it appears that compounds of the tri-carboxylic acid cycle are synthesized from glycine by a scheme similar to that suggested for another species of Pseudomonas grown with glycollate as C source (Kornberg and Gotto, 1961a).