The effect of lipid-depletion on the kinetic properties of rat liver monoamine oxidase-B

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Abstract
The extraction of lipids from rat liver mitochondrial membranes by 2-butanone treatment inhibited the activity of membrane-bound monoamine oxidase -A but not -B. For the -B form, the apparent Michaelis constants of the enzyme towards oxygen and the maximum molecular turnover numbers obtained when β-phenethylamine and benzylamine were used as substrates were not significantly changed by the lipid-depletion procedure, but the values of the Michaelis constant towards benzylamine was significantly increased after lipid- depletion. The differential sensitivity of β-phenethylamine and benzylamine oxidation to inhibition by Tris-HCI was not changed after lípid-depletion. The results are consistent with the hypothesis that the mitochondrial membrane lipids, while essential for the actìvìty of the -A form of the enzyme in rat liver, play a more subtle modulatory role in the activity of the -B form.