Histaminase activity of mesenteric artery of the rat

In rat mesenteric artery homogenates histamine is oxidatively deaminated at high rate whereas putrescine is a poor substrate. The oxidation of histamine appears to be mainly catalyzed by an SSAO enzyme with high affinity for benzylamine (Bz.SSAO). Histamine oxidation is inhibited by B24 (2,5-diethoxy-4-aminomethylpyridine), a selective inhibitor of Bz.SSAO enzymes, and reduced by the presence of benzylamine. The Bz.SSAO enzyme which is present in the rat mesenteric artery is not only able to oxidize histamine, but also methylamine, acetylputrescine and some methylated forms of histamine including 1,4-methylhistamine.