Phospholipid dependency of carp brain and liver mitochondrial monoamine oxidase.

The effects of lipid-protein interactions on carp brain and liver mitochondrial MAO with respect to substrate and inhibitor preference, thermostability and Arrhenius parameters were studied and compared. Treatment with phospholipase A2, C or D decreased MAO activities towards 5-hydroxytryptamine (5-HT), beta-phenylethylamine and tyramine similarly, accompanied by great changes in their apparent affinities for MAO, but not by changes in Vmax values. Minimum phospholipid binding to mitochondria might be essential for enzyme activity. Among these activities, 5-HT deamination was the most sensitive to the changes in mitochondrial phospholipids and bulk lipid phase transition (fluidity). Sensitivity of MAO to clorgyline or l-deprenyl was not affected by these phospholipase treatments. Of the phospholipids tested, only phosphatidylinositol significantly activated MAO activity towards 5-HT in both intact and phospholipase-treated mitochondria.