The enzymatic systems involved in the mammalian metabolism of methylamine.

The metabolism of methylamine has been investigated in the rat in order to elucidate the role of monoamine oxidase (MAO; EC 1.4.3.4) and intestinal bacteria in the metabolism of the compound. In a series of experiments in which short- and long-acting inhibitors of MAO were administered either alone or in combination prior to methyl-[14C]amine hydrochloride injection, the excretion of radioactivity in the expired air and the urine was examined to indirectly assess the role of MAO in the metabolism of methylamine. The data presented provide indirect evidence to demonstrate that the effect of iproniazid, an inhibitor of methylamine oxidation, is mediated through enzyme systems separate from MAO systems which have been invoked as major contributors to metabolism of methylamine by other investigators. The bacterial oxidation of methylamine in the intestine plays a minor role in the overall metabolism of the compound.