ALDH isoenzyme

Ethanal (acetaldehyde), the product of ADH and CYP action on ethanol is the substrate for isoforms of ALDH. Like ADH, ALDH isoenzymes are not entirely substrate specific and will act on aliphatic and aromatic aldehydes to generate the corresponding carboxylic acid. There are nine genes encoding ALDH isoforms and all are subject to polymorphism and the enzyme products of ALDH gene expression are found widely in... 

Toxic acetaldehyde resulting from alcohol oxidation is almost completely oxidized to acetate in the liver cell by aldehyde dehydrogenase (ALDH). For this purpose, various NAD-dependent ALDH isoenzymes are available. Isoenzyme II is bound to the mitochondrial matrix, while isoenzymes I, III and IV are found in the cytosol as well as in the microsomes and, to a lesser degree, in the mitochondria. They also exhibit biochemical differences. Acetaldehyde can be oxidized either by ALDH or by xan-... 

It has been suggested that 17 ALDH isozymes can be found in E coli, and the AldH isoenzyme showed the highest activity among the tested isozymes (AldA, AldB, AldH, YdcW), with high specificity toward Cj and Cj aldehydes. When their activities toward different aldehydes were examined, it was found that AldH showed preference for 3-HPA over isovaleraldehyde, propionaldehyde, butyralde-hyde, and valeraldehyde. Cofactor preference showed that it mainly utilizes NAD" " rather than NADP" ". Furthermore, heavy metals such as Hg- and Ag" " and other metal ions such as K, Na, Cu, and Zn " " have a negative effect on its activity. Maximum activity of the AldH was observed at 37 "C and pH 8.0 [48]. 

An estimated 50% of oriental people have the ALDH-2/2 variant and thus the inactive isoenzyme, which probably accounts for the far lower incidence of heavy drinkers found amongst Chinese and Japanese than, say, Caucasians. Disulfiram is a drug used to treat alcoholics its action is to inhibit ALDH thus creating in heavy or compulsive drinkers an unpleasant and hopefully deterrent reaction. 

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