The metabolism of galactarate, d-glucarate and various pentoses by species of Pseudomonas |
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Authors: | S Dagley and P W Trudgill |
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Institution: | Department of Biochemistry, University of Leeds, and Division of Biochemistry, Department of Chemistry and Chemical Engineering, University of Illinois, Urbana, Ill., U.S.A. |
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Abstract: | 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 Fe2+ ions; the system that acted on d-glucarate was more stable and was stimulated by Mg2+ 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. |
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