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

1. When NAD(+) was present, cell extracts of Pseudomonas (A) grown with d-glucarate or galactarate converted 1mol. of either substrate into 1mol. each of 2-oxoglutarate and carbon dioxide; 70-80% of the gas originated from C-1 of the hexarate. 2. The enzyme system that liberated carbon dioxide from galactarate was inactive in air and was stabilized by galactarate or Fe(2+) ions; the system that acted on d-glucarate was more stable and was stimulated by Mg(2+) ions. 3. When NAD(+) was not added, 2-oxoglutarate semialdehyde accumulated from either substrate. This compound was isolated as its bis-2,4-dinitrophenylhydrazone, and several properties of the derivative were compared with those of the chemically synthesized material. Methods were developed for the determination of 2-oxoglutarate semialdehyde. 4. Synthetic 2-oxoglutarate semialdehyde was converted into 2-oxoglutarate by an enzyme that required NAD(+); the reaction rate with NADP(+) was about one-sixth of that with NAD(+). 5. For extracts of Pseudomonas (A) grown with d-glucarate or galactarate, or for those of Pseudomonas 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. 6. Extracts of Pseudomonas 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.