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pubmed:abstractText |
In Peptostreptococcus elsdenii, a three-component flavoprotein electron transfer system catalyzes the oxidation of lactate and the reduction of crotonyl-coenzyme A (CoA). Spectral evidence showed that D-lactate dehydrogenase, when reduced by D-lactate, was able to reduce butyryl-CoA dehydrogenase, but only in the presence of the electron-transferring flavoprotein. Reduced nicotinamide adenine dinucleotide could replace reduced D-lactate dehydrogenase. A reconstituted system, containing the three partially purified enzymes, excess D-lactate, and a limiting amount of crotonyl-CoA, reduced the crotonyl-CoA to butyryl-CoA, but only if all components were present. The electron-transferring flavoprotein activity, purified 22-fold, was separated into two major flavoprotein components, A and B, after polyacrylamide gel electrophoresis. Elution of the proteins and subsequent kinetic assays of the eluates showed that component B catalyzes the reduction of butyryl-CoA dehydrogenase by reduced D-lactate dehydrogenase, whereas component A does not. Both A and B catalyzed the reduction of butyryl-CoA dehydrogenase by reduced nicotinamide adenine dinucleotide. The results suggest that the D-lactate dehydrogenase-dependent reduction involves a heretofore unrecognized component of the electron-transferring protein group which may utilize an unusual flavin, 6-hydroxy-7,8-dimethyl-10-(ribityl-5'-adenosine diphosphate)-isoalloxazine.
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pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, P.H.S.,
Research Support, U.S. Gov't, Non-P.H.S.
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