Identification of carboxylation enzymes and characterization of a novel four-subunit pyruvate:flavodoxin oxidoreductase from Helicobacter pylori.
نویسندگان
چکیده
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.
منابع مشابه
Helicobacter pylori porCDAB and oorDABC genes encode distinct pyruvate:flavodoxin and 2-oxoglutarate:acceptor oxidoreductases which mediate electron transport to NADP.
Helicobacter pylori, a major cause of human gastric disease, is a microaerophilic bacterium that contains neither pyruvate nor 2-oxoglutarate dehydrogenase activity. Previous studies (N. J. Hughes, P. A. Chalk, C. L. Clayton, and D. J. Kelly, J. Bacteriol. 177:3953-3959, 1995) have indicated that the major routes for the generation of acetyl coenzyme A (acetyl-CoA) and succinyl-CoA are via pyru...
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ورودعنوان ژورنال:
- Journal of bacteriology
دوره 177 14 شماره
صفحات -
تاریخ انتشار 1995