Effects of enzyme/substrate ratio and of cofactors on the oxidation products of indole-03-acetic acid catalyzed by peroxidase

Abstract

During the oxidation of indole-03-acetic acid catalyzed by peroxidase, the relative amounts of the products closely depends on the enzyme/substrate ratio.In the absence of cofactors, high enzyme/substrate ratio induces a rise in the level of indole-03-aldehyde and indole-03-methanol, and a drop in that of oxindoles.2,4-dichlorophenol, although a very efficient cofactor, promotes inhibition of the oxidation after a few minutes, presumably through the formation of a phenol-derivative inhibitor.2-4-dichlorophenol also inhibits the production of oxindoles at all stages.Both inhibitory effects are abolished by a low concentration of enzyme.Mn2+, itself a weak inhibitor, synergizes the catalytic effect of 2,4-dichlorophenol, perhaps by preventing the formation of the inhibitor.The results are discussed against more widely accepted mechanisms of indole-03-acetic acid oxidation.