Effect of antioxidants (digoxin, quercetin, and ascorbic acid) on catalytic properties of horseradish peroxidase.
Antioxidants (digoxin, quercetin, and ascorbic acid) inhibited the oxidation of o-dianisidine catalyzed by horseradish peroxidase. Digoxin bound with the enzyme-substrate complex which included a stable semioxidized product of o-dianisidine and inhibited horseradish peroxidase by the anticompetitive pattern, while the enzyme inhibition by quercetin followed the mixed pattern. The oxidation of ascorbic acid and o-dianisidine with their combined presence in the reaction mixture was differentiated. o-Dianisidine was oxidized after the oxidation of 90-100% of ascorbic acid was completed. The rate of peroxidase oxidation of ascorbic acid in the presence of o-dianisidine was more than two orders higher than the rate of its individual oxidation and 1.5-2.0 times higher than the rate of o-dianisidine oxidation. Feasible inhibition mechanisms of peroxidase oxidation of o-dianisidine are discussed.
Yakutsk State Agricultural Academy, Yakutsk, 677002, Russia.
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Rogozhin
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Verkhoturov
D000975:Antioxidants / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000494:pharmacology; D002384:Catalysis; D003962:Dianisidine / Q000378:metabolism; D004077:Digoxin / Q000494:pharmacology; D006735:Horseradish Peroxidase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D011794:Quercetin / Q000494:pharmacology
D000975:Antioxidants; D004077:Digoxin; D011794:Quercetin; D006735:Horseradish Peroxidase; D003962:Dianisidine; D001205:Ascorbic Acid