THE METABOLISM OF GALACTARATE, d-GLUCARATE AND VARIOUS PENTOSES BY SPECIES OF PSEUDOMONAS

Abstract

When nicotinamide adenine dinucleotide (NAD+) was present, cell extracts of Pseudomonas (A) grown with D-glucarate or galactarate converted 1 mol.of either substrate into 1 mol. each of 2-oxoglutarate and CO2; 70-80% of the gas originated from C-1 of the hexarate. The enzyme system that liberated CO2 from galactarate was inactive in air and was stabilized by galactarate or Fe2+ ions; the system that acted on D-glucarate was more stable and was stimulated by Mg2+ ions. When NAD+ was not added, 2-oxoglutarate semialdehyde accumulated from either substrate. This compound was isolated as its bis-2,4-dinitrophenylhydrazone. Synthetic 2-oxoglutarate semialdehyde was converted into 2-oxoglutarate by an enzyme that required NAD+; the reaction rate with nicotinamide adenine dinucleotide phosphate (NAPD+) was about 1/6 of that with NAD+. For extracts of Pseudomonas (A) grown with D-glucarate or galactarate, or for those of P. fragi grown with L-arabinose or D-xylose, specific activities of 2-oxoglutarate semialdehyde-NAD oxidoreductase were much higher than for extracts of the organisms grown with (+)-tartrate and D-glucose respectively. Extracts of P. fragi grown with L-arabinose or D-xylose converted L-arabonate or D-xylonate into 2-oxoglutarate when NAD+ was added to reaction mixtures and into 2-oxoglutarate semialdehyde when NAD+ was omitted.