The gnd gene encoding a novel 6-phosphogluconate dehydrogenase and its adjacent region of Actinobacillus actinomycetemcomitans chromosomal DNA

A 10-kb DNA fragment containing the gnd gene from Actinobacillus actinomy-cetemcomitans Y4 was isolated and sequenced. The structural gnd gene codes for 6-phosphogluconate dehydrogenase that consists of 484 amino acids. In contrast to the gnd gene in Escherichia coli, Salmonella typhimurium, or Klebsiella pneumoniae, the gnd gene of A. actinomycetemcomitans was not located in the rfb or cps operon. The zwf gene encoding glucose 6-phosphate dehydrogenase, which is another enzyme consisting of pentose-phosphate pathway, sided at 3.8-kb upstream from the gnd gene. A phylogenetic tree based on sequence analyses showed higher homology of 6-phospho-gluconate dehydrogenase of A. actinomycetemcomitans with the eucaryotic enzymes rather than with bacterial enzymes.