Association between I(2) binding sites and monoamine oxidase-B activity in platelets

An I(2) imidazoline binding site on monoamine oxidase-B (MAO-B) is known to be encoded by a noncatalytic part of the enzyme, different from that which recognizes mechanism-based inhibitors. Herein, the relationship between I(2)-imidazoline binding sites and MAO-B activity has been assessed using a semi-purified source of MAO-B: platelet mitochondrial membranes. A positive correlation between I(2) sites and MAO-B activity was observed (r = 0.61, P = 0.0016) among 24 human subjects. Nevertheless, the variance in MAO-B activity cannot be completely accounted for in relation to I(2) sites. Therefore, I(2) density and MAO-B activity are only weakly correlated in platelets.