FORMIC DEHYDROGENASE AND THE HYDROGENLYASE ENZYME COMPLEX IN COLI-AEROGENES BACTERIA

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Abstract
The mechanism of formate decomposition to H2 and CO2 (hydrogenlyase activity) in coli-aerogenes bacteria was investigated and further direct evidence obtained that the reaction is catalyzed by a multi-enzyme system consisting of formic dehydrogenase, hydrogenase, and one or two intermediate factors. The formic dehydrogenase component required is a soluble metalloenzyme capable of reducing one-electron dyes of low redox potential (viologens) in the presence of formate and is produced only during anaerobic growth. Partially purified formic dehydrogenase (viologen) readily couples with particulate hydrogenase preparations, obtained from another non-gas producing variant, to reconstitute an active hydrogenlyase system. Formic dehydrogenase (methylene blue) is incapable of coupling in this manner. Further evidence is presented that the particles contain, in addition to hydrogenase, an intermediate carrier (X2) necessary for electron transport from formic dehydrogenase (viologen) to hydrogenase. Comparison of the hydrogenlyase system reconstructed by mixing "complementary" preparations from the two non-gas producers with the system present in extracts of normal Escherichia coli indicates that they are identical in respects. Many properties of overall hydrogenlyase activity are referable to effects on formic dehydrogenase (viologen), particularly in systems wherein the latter is a limiting component. The present results are discussed in relation to the enzymatic constitution of normal and non-gas producing bacteria of the coli-aerogenes group.

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