[Effect of protein denaturing reactions on retardation of the activity of rat liver mitochondrial monoamine oxidase by clorgyline and deprenyl].

The denaturating effects of urea on clorgyline-produced inhibition of serotonin and tyramine deamination and deprenyl-produced inhibition of beta-phenylethylamine and tyramine oxidation were studied. It was shown that after preincubation of mitochondria with 1 and 2 M urea the intensity of inhibition by clorgyline and deprenyl of oxidation of these amines was not changed. With urea concentration of 3 and 4 M the inhibitory effect of clorgyline on deamination of serotonin and tyramine was increased, while that of deprenyl on oxidation of beta-phenylethylamine and tyramine was decreased. As a result of mitochondria treatment with 3 and 4 M urea the selectivity in inhibition by clorgyline of serotonin and tyramine deamination typical for intact mitochondria was reduced in the case of 3 M urea and eliminated in the case of 4 M urea. In intact mitochondria the intensity of inhibition by clorgyline of tyramine deamination in the presence of benzyl alcohol (competitive reversible MAO inhibitor) was increased, but the additive effect was not achieved. However, after preincubation of mitochondria with 3 M urea the summation of the inhibitory effects of clorgyline and benzyl alcohol was observed. The data obtained provide further evidence for the important role of spatial configuration of the monoamine oxidase molecule; the data are discussed in terms of arrangement on the protein molecule surface of the essential groups involved in the binding and deamination of amines for the inhibitory effects of clorgyline and deprenyl.