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. 1994 Jun;60(6):2065–2068. doi: 10.1128/aem.60.6.2065-2068.1994

The DeLey-Doudoroff Pathway of Galactose Metabolism in Azotobacter vinelandii

T Y Wong 1,*, X-T Yao 1
PMCID: PMC201602  PMID: 16349292

Abstract

Azotobacter vinelandii cell extracts reduced NAD+ and oxidized d-galactose to galactonate that subsequently was converted to 2-keto-3-deoxy-galactonate. Further metabolism of 2-keto-3-deoxy-galactonate required the presence of ATP and resulted in the formation of pyruvate and glyceraldehyde 3-P. Radiorespirometry indicated a preferential release of CO2 at the first carbon position of the d-galactose molecule. This suggested that Azotobacter vinelandii metabolizes d-galactose via the DeLey-Doudoroff pathway. The first enzyme of this pathway, d-galactose dehydrogenase, was partially characterized. It has a molecular weight of about 74,000 Da and an isoelectric point of 6.15. The pH optimum of the galactose dehydrogenase was about 9. The apparent Kms for NAD+ and d-galactose were 0.125 and 0.56 mM, respectively. Besides d-galactose, the active fraction of this galactose dehydrogenase also oxidized l-arabinose effectively. The electron acceptor for d-galactose or l-arabinose oxidation, NAD+, could not be replaced by NADP+. These substrate specificities were different from those reported in Pseudomonas saccharophila, Pseudomonas fluorescens, and Rhizobium meliloti.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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