Properties of mammalian tissue-bound semicarbazide-sensitive amine oxidase: possible clues to its physiological function?

Semicarbazide-sensitive amine oxidase (SSAO), occurs not only in vascular smooth muscle but also in other cell types (e.g. adipocytes, chondrocytes, odontoblasts), probably in the plasma membrane. Although certain aromatic biogenic amines (e.g. tryptamine, tyramine, beta-phenyl-ethylamine) may be endogenous substrates for SSAO in species such as the rat, the weak activity of SSAO in human tissues towards these amines makes this less likely in man. However SSAO in human and rat vascular homogenates readily converts the aliphatic biogenic amines methylamine and aminoacetone to formaldehyde and methylglyoxal, respectively. Also the xenobiotic aliphatic amine allylamine produces cardiovascular damage in experimental animals by a mechanism which involves its deamination by SSAO to acrolein. Further metabolism of these toxic aliphatic aldehydes may involve glutathione-dependent pathways. Thus, SSAO may be involved not only in the removal of physiologically-active endogenous/xenobiotic amines, but resulting metabolite (aldehyde/H2O2?) formation could also influence cellular function.