title: The reduction of allyl alcohols by Clostridium species is catalyzed by the combined action of alcohol dehydrogenase and enoate reductase.
abstract: Cells, as well as crude extracts of Clostridium kluyveri or Clostridium spec. La 1, catalyze the hydrogenation of (E)- or (Z)-2-butenol to n-butanol. No single enzyme could be detected which directly accomplishes this reaction. It turned out that the reduction occurs as follows: 2-butenol leads to 2-butenal leads to n-butanal leads to n-butanol. The first step is catalyzed by the NAD-dependent alcohol dehydrogenase in C. kluyveri, the second by the recently detected enoate reductase which reduces not only nonactivated alpha, beta-unsaturated acylates but also alpha, beta-unsaturated aldehydes in a NADH-dependent reaction and the third step is again catalyzed by alcohol dehydrogenase. In Clostridium La 1 the alcohol dehydrogenase is NADP-dependent. The rate of the reduction of 2-butenol to n-butanol depends not only on the enzymes, but also on the ratio NAD(P)/NAD(P)H. In the presence of methylviologen cation radical which is formed by the reduction of methylviologen by the system H2/hydrogenase, the ratio NAD(P)/NAD(P)H is too small for the dehydrogenation of 2-butenol to 2-butenal. This explains the antagonistic effect of methylviologen in the hydrogenation of allyl alcohols and 2-enoates by both Clostridium species. Furthermore, the mechanism explains the finding that from a preparative point of view ethanol is a better electron donor than hydrogen for the stereospecific reduction of allyl alcohols.
mesh_terms: D000433:1-Propanol / Q000378:metabolism; D000429:Alcohol Oxidoreductases / Q000378:metabolism*; D003013:Clostridium / Q000201:enzymology*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D007700:Kinetics; D009243:NAD / Q000032:analysis; D009249:NADP; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D044925:Oxidoreductases Acting on CH-CH Group Donors; D020005:Propanols; D013379:Substrate Specificity
chemical_list: D005231:Fatty Acids, Unsaturated; D020005:Propanols; D009243:NAD; C006463:allyl alcohol; D009249:NADP; D000433:1-Propanol; D010088:Oxidoreductases; D000429:Alcohol Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; C019367:2-enoate reductase