HUMAN-LIVER ALCOHOL-DEHYDROGENASE ISOZYMES - REDUCTION OF ALDEHYDES AND KETONES

被引：55

作者：

DEETZ, JS ^{[1
]}

LUEHR, CA ^{[1
]}

VALLEE, BL ^{[1
]}

机构：

[1] HARVARD UNIV, SCH MED, CTR BIOCHEM & BIOPHYS SCI & MED, BOSTON, MA 02115 USA

来源：

BIOCHEMISTRY | 1984年 / 23卷 / 26期

关键词：

D O I：

10.1021/bi00321a084

中图分类号：

Q5 [生物化学]; Q7 [分子生物学];

学科分类号：

071010 ; 081704 ;

摘要：

The class I (.alpha., .beta.1, .gamma.1 and .gamma.2), II (.pi.) and III (.chi.) isozymes of human liver alcohol dehydrogenase (ADH) were isolated as electrophoretically homogeneous preparations to examine their kinetics of aldehyde and ketone reduction. While the oxidation of a wide variety of alcohols by ADH has been investigated extensively, the reduction of aldehydes and ketones has received much less attention even though the equilibrium favors the latter process. For each isozyme, the Km and kcat values were measured at pH 7.0 with acetaldehyde, pentanal, octanal, benzaldehyde and cyclohexanone as substrates. Activity could not be detected with succinic semialdehyde and betaine aldehyde for any of the isozymes. The nonenzymatic hydration, oxidation and aldol condensation of aldehydes in aqueous solutions present serious experimental obstacles in determining the isozymes'' kinetic constants. The effects of these reactions on the enzymatic parameters were studied and compensated for. Km for all class I and II isozymes vary by more than 8000-fold, from less than 1 .mu.M for .beta.1.gamma.1 and .beta.1.beta.1 with octanal to 8.3 mM for .pi.-ADH for acetaldehyde. However, with any given aldehyde, these values vary by less than 40-fold, and the constants are approximately equal to Km values reported previously for the corresponding alcohols. In contrast, Km values for .chi.-ADH are extremely high and could be determined accurately only for octanal (75 .mu.M). The kcat values for class I and II isozymes range from 21 min-1 for .beta.1.beta.1 with cyclohexanone to 3400 min-1 for .beta.1.gamma.2 with octanal and are generally an order of magnitude greater than those for the alcohols. However, the .beta.1.beta.1 isozyme catalyzes both the reduction of aldehydes and the oxidation of alcohols at turnover rates significantly lower than those of other class I forms. Hence, in principle, poor oxidase activity does not necessarily imply good reductase activity.

引用

页码：6822 / 6828

页数：7

共 44 条

[11]

CARNAHAN B, 1969, APPLIED NUMERICAL ME, P282

[12]

Cleland W W, 1979, Methods Enzymol, V63, P103

[13]

CLELAND WW, 1967, ADV ENZYMOL RAMB, V29, P1

[14]

CORNISHBOWDEN A, 1976, PRINCIPLES ENZYME KI, P142

[15]

DITLOW CC, 1984, BIOCHEMISTRY

[16] STRUCTURAL STUDIES OF HORSE LIVER ALCOHOL-DEHYDROGENASE - CO-ENZYME, SUBSTRATE AND INHIBITOR BINDING [J].

EKLUND, H .

PHARMACOLOGY BIOCHEMISTRY AND BEHAVIOR, 1983, 18 :73-81

[17]

FROST AA, 1961, KINETICS MECHANISM, P185

[18]

HASTINGS JW, 1963, J BIOL CHEM, V238, P3100

[19]

JONES JB, 1976, TECH CHEM NY, V10, P107

[20] HUMAN-LIVER ALCOHOL-DEHYDROGENASE - AMINO-ACID SUBSTITUTION IN THE BETA-2-BETA-2 ORIENTAL ISOZYME EXPLAINS FUNCTIONAL-PROPERTIES, ESTABLISHES AN ACTIVE-SITE STRUCTURE, AND PARALLELS MUTATIONAL EXCHANGES IN THE YEAST ENZYME [J].

JORNVALL, H ;

HEMPEL, J ;

VALLEE, BL ;

BOSRON, WF ;

LI, TK .

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA-BIOLOGICAL SCIENCES, 1984, 81 (10) :3024-3028

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