Identification of a human stomach alcohol dehydrogenase with distinctive kinetic properties.
A new form of alcohol dehydrogenase, designated mu-alcohol dehydrogenase, was identified in surgical human stomach mucosa by isoelectric focusing and kinetic determinations. This enzyme was anodic to class I (alpha, beta, gamma) and class II (pi) alcohol dehydrogenases on agarose isoelectric focusing gels. The partially purified mu-alcohol dehydrogenase, specifically using NAD+ as cofactor, catalyzed the oxidation of aliphatic and aromatic alcohols with long chain alcohols being better substrates, indicating a barrel-shape hydrophobic binding pocket for substrate. mu-Alcohol dehydrogenase stood out in high Km values for both ethanol (18 mM) and NAD+ (340 microM) as well as in high Ki value (320 microM) for 4-methylpyrazole, a competitive inhibitor for ethanol. mu-Alcohol dehydrogenase may account for up to 50% of total stomach alcohol dehydrogenase activity and appeared to play a significant role in first-pass metabolism of ethanol in human.
Yin
S J
SJ
Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan, Republic of China.
Wang
M F
MF
Liao
C S
CS
Chen
C M
CM
Wu
C W
CW
D000426:Alcohol Dehydrogenase / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D000431:Ethanol; D000077604:Fomepizole; D005753:Gastric Mucosa / Q000201:enzymology*; D006801:Humans; D066298:In Vitro Techniques; D007525:Isoelectric Focusing; D007700:Kinetics; D009243:NAD; D011720:Pyrazoles / Q000494:pharmacology; D013379:Substrate Specificity
D011720:Pyrazoles; D009243:NAD; D000431:Ethanol; D000077604:Fomepizole; D000426:Alcohol Dehydrogenase