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J. Bacteriol., Jul 1995, 3953-3959, Vol 177, No. 14
NJ Hughes, PA Chalk, CL Clayton and DJ Kelly
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 6.4.1.2) and malic enzyme (EC 1.1.1.40) activities were
detected, whereas pyruvate carboxylase (EC 6.4.1.1), phosphoenolpyruvate
carboxylase (EC 4.1.3.1) and phosphoenolpyruvate carboxykinase (EC
4.1.1.49) 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 1.2.7.1), 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.
Copyright © 1995, American Society for Microbiology
Identification of carboxylation enzymes and characterization of a novel four-subunit pyruvate:flavodoxin oxidoreductase from Helicobacter pylori
Department of Molecular Biology and Biotechnology, University of Sheffield, United Kingdom.
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