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J Bacteriol. 1995 Jul;177(14):3953-9.

Identification of carboxylation enzymes and characterization of a novel four-subunit pyruvate:flavodoxin oxidoreductase from Helicobacter pylori.

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Department of Molecular Biology and Biotechnology, University of Sheffield, United Kingdom.


The enzyme activities responsible for carboxylation reactions in cell extracts of the gastric pathogen Helicobacter pylori have been studied by H14CO3- fixation and spectrophotometric assays. Acetyl coenzyme A carboxylase (EC and malic enzyme (EC activities were detected, whereas pyruvate carboxylase (EC, phosphoenolpyruvate carboxylase (EC and phosphoenolpyruvate carboxykinase (EC activities were absent. However, a pyruvate-dependent, ATP-independent, and avidin-insensitive H14CO3- fixation activity, which was shown to be due to the isotope exchange reaction of pyruvate:flavodoxin oxidoreductase (EC, was present. The purified enzyme is composed of four subunits of 47, 36, 24, and 14 kDa. N-terminal sequence analysis showed that this enzyme is related to a recently recognized group of four-subunit pyruvate:ferredoxin oxidoreductases previously known only from hyperthermophiles. This enzyme from H. pylori was found to mediate the reduction of a number of artificial electron acceptors in addition to a flavodoxin isolated from H. pylori extracts, which is likely to be the in vivo electron acceptor. Indirect evidence that the enzyme is capable of in vitro reduction of the anti-H. pylori drug metronidazole was also obtained.

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