Identification of an endogenous electron donor for biohydrogenation as alpha-tocopherolquinol.
Four fluorescent compounds present in solvent extracts of Butyrivibrio fibrisolvens could serve as electron donors for the biohydrogenation of cis-9,trans-11-octadecadienoate in the presence of dithionite, which was itself inactive. One of the compounds was identified as alpha-tocopherolquinol and another as alpha-tocopherolquinone. A partially purified soluble enzyme preparation from B. fibrisolvens catalyzed the reduction of alpha-tocopherolquinone to alpha-tocopherolquinol in the presence of NADH with a stoichiometry of 1:1. The ratio of alpha-tocopherolquinone produced to fatty acid reduced was 2:1 when the tocopherol derivatives were extracted aerobically. When the extraction was carried out anaerobically, the ratio was 1. It is suggested that the oxidation of 2 molecules of alpha-tocopherolquinol, each to the semiquinone, provides the electrons required for the reduction of the cis-bond of the conjugated dienoic fatty acid. Although alpha-tocopherol, phylloquinol, and reduced menadione are inactive, ubiquinol-4, ubiquinol-10, and trimethylhydroquinone show about one-half the activity of alpha-tocopherolquinol. Plastoquinol and trimethylphytylbenzoquinol are as active as alpha-tocopherolquinol.
D000693:Anaerobiosis; D004227:Dithionite / Q000494:pharmacology; D004579:Electron Transport; D006089:Gram-Negative Anaerobic Bacteria / Q000378:metabolism*; D007700:Kinetics; D009243:NAD; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism; D013053:Spectrophotometry; D014810:Vitamin E / Q000031:analogs & derivatives* / Q000378:metabolism; D024502:alpha-Tocopherol / Q000031:analogs & derivatives*
D009243:NAD; D014810:Vitamin E; C024838:alpha-tocopherol quinol; D004227:Dithionite; D010088:Oxidoreductases; C024853:cis-9,trans-11-octadecadienoate reductase; D024502:alpha-Tocopherol