Semicarbazide-sensitive amine oxidase from the smooth muscles of dog aorta and trachea: activation by the MAO-A inhibitor clorgyline.

Semicarbazide-sensitive amine oxidase (SSAO) has been identified in the dog trachea and aorta smooth muscles. The dog SSAO is blocked by hydrazine inhibitors. SSAOs from several different vascular smooth muscle sources, such as the rat and bovine aorta, and human umbilical artery, as well as the bovine plasma, are insensitive to the MAO-A inhibitor clorgyline; the dog SSAO on the other hand is significantly activated by clorgyline. Two methods, i.e. radioenzymatic and fluorometric methods, have been applied to substantiate this clorgyline-induced activation. The activation was detected with respect to the deamination of different substrates, such as benzylamine, beta-phenylethylamine and longer carbon chain aliphatic amines, but not with respect to methylamine. The clorgyline effect is reversible, non-competitive and time-independent; it depends on electrostatic and hydrophobic interactions between clorgyline and hydrophobic regions of the dog SSAO enzyme.