[Unusual inhibition of monoamine oxidase activity induced by clorgyline]

The phenomenology of inhibition of FAD-containing type A monoamine oxidase by clorgyline solutions containing negligibly small amounts of clorgyline that are insufficient for stoichiometric covalent blocking of a perceptible amount of the coenzyme was studied. The nature of this phenomenon consists in the fact that at monoamine oxidase concentrations of about 10(-8) M, more than 50% of the enzyme activity in inhibited by clorgyline (less than or equal to 10(-10) M), although is accordance with a well-defined mechanism after monoamine oxidase-catalyzed tautomerization clorgyline presumably interacts with FAD at a 1:1 stoichiometric ratio. This effect termed as secondary inhibition seems to be induced not by clorgyline proper, not by changes in the solvent induced by this compound. In other words, clorgyline may initiate the synthesis of a new hypothetical inhibitor (IIC) in aqueous media which causes a reversible inhibition of the same specific inhibitory site of the enzyme. This site is responsible for the initial binding of acetylene inhibitors and catalyzes the formation of their allenic derivatives.