Aldehyde dehydrogenase

About: Aldehyde dehydrogenase is a research topic. Over the lifetime, 3365 publications have been published within this topic receiving 107683 citations.

New pathway of conversion of pyridoxal to 4-pyridoxic acid.

Abstract: The only enzyme demonstrated so far to catalyze the formation of 4-pyridoxic acid, the final excretory product of vitamin B6, was aldehyde oxidase. In this paper we have presented an evidence that another enzyme, NAD+-dependent aldehyde dehydrogenase, is capable of catalyzing this reaction. Rat mutants with high, low and no aldehyde oxidase activity excrete the same amount of isotope after a single injection of 3H-pyridoxol in a 12-day experiment; 4-pyridoxic acid is also present in the urine of animals without aldehyde oxidase activity. There is no correlation between the proportion of the excreted acid and the amount of pyridoxal excreted, after the injection of a single dose of the aldehyde form. The Km values for pyridoxal and NAD+, at pH 9.6, have been found to be 75 and 260 mumol/l, respectively. NAD+-dependent pyridoxal dehydrogenase was partially purified from the rat tissues, and the following specific enzyme activities (nmol-min-1-mg-1 protein) were found: red blood cell 71.5 +/- 3.0, intestine 64.9 +/- 9.0, muscle 61.4 +/- 1.6, brain 39.5 +/- 6.0, liver 34.4 +/- 3.3, kidney 21.1 +/- 5.6, heart 18.8 +/- 0.9, and lung 6.5 +/- 2.0. This is believed to be the first report demonstrating pyridoxal oxidation, catalyzed by an NAD+-dependent aldehyde dehydrogenase.

Alcohol dehydrogenase: enzymology and metabolism.

Abstract: Alcohol dehydrogenase (ADH), the principal enzyme responsible for ethanol oxidation, constitutes a complex family in humans. Based on structural and kinetic features, ADH can be divided into five classes. Low-Km class I beta-ADH and gamma-ADH show genetic polymorphism among racial populations. The allozymes exhibit distinct maximal activities due to single amino acid exchanges at different sites in the coenzyme-binding domain. Class IV mu-ADH also shows ethnic variability: it is detected in the stomach mucosa of Caucasians but not detectable in about 70% of Orientals. Class I, II, IV and V ADH isozymes exhibit tissue-specific distribution. Approximately 50% of Orientals lack the activity of the mitochondrial low-Km aldehyde dehydrogenase (ALDH2). Ethanol- and acetaldehyde-oxidizing activities of the liver, lung, and gastrointestinal tract appear to be correlated with their isozyme patterns of ADH and ALDH and with the allozymes. The frequencies of the alleles ADH(2)2 and ADH(3)1, coding for the high-Vmax beta 2- and gamma 1-ADH respectively, and of the mutant ALDH(2)2 in the Oriental subjects with alcoholism or alcoholic cirrhosis are significantly lower than those in healthy controls. These genotyping results support the current notion that genetic variation in ADH and ALDH may influence drinking behavior and susceptibility for alcoholism and possibly alcohol-induced organ injury by modulating the rate of metabolism of ethanol and acetaldehyde.