Inactivation of yeast alcohol dehydrogenase by alkylperoxyl radicals. Characteristics and influence of nicotinamide-adenine dinucleotides.
The study of the interaction of alkylperoxyl radicals generated by the aerobic thermolysis of 2,2'-azobis(2-amidinopropane) (AAP) with yeast alcohol dehydrogenase (YADH) revealed a high reactivity of the enzyme, with an average of about 20 radicals per added YADH tetramer being needed to elicit its total inactivation. NAD+ enhanced YADH inactivation at NAD+/YADH molar ratios from 0.25 to 1, decreasing the rate of the process when added in excess to the enzyme concentration. At NADH/YADH molar ratios greater than 1, NADH exhibited a protective effect characterized by a poorly defined induction time and lower inactivation rates, which progressively increased during the reaction period. These changes occurred concomitantly with the oxidation of NADH into NAD+, which might counteract the protective effect of NADH. Under similar conditions, NADP+ did not modify AAP-induced YADH inactivation, while NADPH exhibited a modest protection at NADPH/YADH molar ratios greater than 1. It is concluded that YADH inactivation by alkylperoxyl radicals is strongly dependent on the redox state of the NADH-NAD+ couple, as the rates of the process at different time intervals inversely correlate with the respective NADH/NAD+ ratios.
Videla
L A
LA
Departamento de Ciencias Biológicas, Facultad de Medicina, Universidad de Chile, Santiago.
Salim-Hanna
M
M
Lissi
E A
EA
D000426:Alcohol Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000578:Amidines / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005609:Free Radicals; D007700:Kinetics; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D010545:Peroxides / Q000494:pharmacology*; D015003:Yeasts / Q000201:enzymology*
D000578:Amidines; D005609:Free Radicals; D010545:Peroxides; D009243:NAD; C049375:perhydroxyl radical; D009249:NADP; C046728:2,2'-azobis(2-amidinopropane); D000426:Alcohol Dehydrogenase