Effect of Phospholipid Depletion by Phospholipases on the Properties and Formation of the Multiple Monoamine Oxidase Forms in the Rat Liver

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Abstract
The effect of phospholipid depletion by phospholipases on the properties and formation of monoamine oxidase [EC 1.4.3.4] A and B was investigated. The enzyme was solubilized, partially purified, treated with phospholipases and subjected to gel filtration to reduce the amount of enzyme-associated phospholipids. Phospholipase A treatment of the purified monoamine oxidase fraction had no effect on the deprenil inhibition pattern or the observed transition temperatures in the Arrhenius plots. The rate of enzyme inactivation by heat and trypsin were greatly increased but differences in rates of inactivation of monoamine oxidase A and B were still observed. Phospholipase C treatment of the enzyme fraction had no effect on the deprenil inhibition pattern, Arrhenius plots, heat stability or trypsin digestibility. The inhibition pattern of membrane-bound monoamine oxidase and the phospholipase-treated fractions by propargylamine showed a reduced substrate specificity compared to deprenil suggesting a hydrophobic region in the enzyme is a factor involved in the structural differences of monoamine oxidase A and B.