The widespread distribution of
enzymes classed as
semicarbazide-sensitive
amine oxidases (SSAO
enzymes) throughout a very wide range of eukaryotic as well as prokaryotic organisms encourages the aspirations of those who wish to demonstrate physiological, pathological or pharmacological importance. Such
enzymes are found in several tissues of mammals, both freely soluble, as in blood plasma, and membrane-bound, for example, in smooth muscle and adipose tissue. While they are capable of deaminating many
amines with the production of an
aldehyde and
hydrogen peroxide, doubt still surrounds the identity of the most important endogenous substrates for these
enzymes. At present,
methylamine and
aminoacetone appear to head the list of candidates. The possibility that SSAO
enzymes can convert
amine substrates to highly toxic metabolites is illustrated by the production of
acrolein from the
xenobiotic amine,
allylamine and
formaldehyde and
methylglyoxal from
methylamine and
aminoacetone, respectively. Activities of SSAO
enzymes may be influenced by physiological changes, such as pregnancy or pathologically by disease states, including diabetes, tumours and
burns. Increased deamination of
aminoacetone by tissue and plasma SSAO
enzymes as a result of its increased production from
L-threonine in conditions such as exhaustion,
starvation and
diabetes mellitus may be harmful. Such dangers could be mitigated either physiologically by a compensatory reduction in SSAO activity or pharmacologically by treatment with inhibitors of SSAO.