Inhibition of bovine plasma semicarbazide-sensitive amine oxidase by caffeine.

Semicarbazide-sensitive amine oxidase (SSAO) is a copper-containing enzyme that catalyzes the oxidative deamination of endogenous and exogenous primary amines. SSAO exists in mammals both as a plasma-soluble and as a membrane-bound form, and its active site is able to come into contact with numerous xenobiotic, amine-containing compounds. The kinetic studies performed in this work showed that caffeine inhibition of bovine serum amine oxidase was noncompetitive when benzylamine was used as substrate and mixed when the substrate used was methylamine. Since caffeine contains an imidazole ring, it cannot be excluded that it might bind to an inhibitory imidazoline-binding site on SSAO.