Alcohol dehydrogenase occurrence

Alcohol dehydrogenases can be subdivided with respect to various criteria, two of which are in particular relevant for the application of these enzymes first structural and protein chemical data, especially subunit size and occurrence of metal ions, and second the stereochemical course of the catalyzed reaction and the consequential chirality of the formed alcohol. 

NADPH. In a number of examples it has been demonstrated that cyclic sesquiter-penoids result from 2-trans-FFP by dephosphorylation and conversion into 2-cis-farnesol (and hence presumably 2-c/5-FPP) via a redox system. However, in the present case farnesol was not a substrate and no tracer could be demonstrated to be associated with the farnesals. The fact that the added hydrogen came from the opposite face of NADPH to that utilized in common redox systems e.g. liver alcohol dehydrogenase) may indicate that a totally different type of mechanism occurs from that previously proposed for the trans to cis conversion, and the occurrence of a novel cyclopropyl intermediate was suggested (Scheme 12). 

Previously known substrates have been reviewed earlier (f) as well as the widespread occurrence of alcohol dehydrogenase in nature. Alcohols, including ethanol, produced in the intestinal tracts mainly by bacterial actions, are found in the portal vein. One physiological function of liver alcohol dehydrogenase may be to metabolize these products 8). 

Horse liver alcohol dehydrogenase was first crystallized by Bonnichsen and Wasson in 1948 (34) An acidic minor component was isolated by Dalziel (35), and different forms were later shown to exist (36,37). Neither of these studies revealed the true isozyme pattern of horse liver alcohol dehydrogenase, and an increasing number of different molecular forms have since been characterized. The multiplicity is a result of the synthesis of different types of subunits as well as of the occurrence of secondary modified forms. 

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