Interaction between cytosolic monoamine oxidase and spin-labeled amphetamine and its modification by clorgyline and pargyline.

Interactions between a monoamine oxidase (monoamine: oxygen oxidoreductase deaminating, EC 1.4.3.4) obtained from rat liver cytosol by high speed centrifugation and a biologically active, spin labeled analog of amphetamine have been analyzed. The acetylenic monoamine oxidase inhibitors, pargyline and clorgyline, have been used to modulate the binding of spin labeled amphetamine. Broadening of electron spin resonance lines induced by immobilization of the probe on binding has been used to determine the concentration of bound probe. Pargyline was found to inhibit binding of spin labeled amphetamine by cytosolic monoamine oxidase. Bound spin labeled amphetamine was also displaceable by pargyline. In contrast, clorgyline enhanced the binding of spin labeled amphetamine to the cytosolic monoamine oxidase preparation. Inhibition or enhancement of amphetamine binding was very rapid and occurred during the reversible stage of interaction between the enzyme and the acetylenic compounds.