Semicarbazide-sensitive amine oxidase (SSAO): present and future.

Although the existence of plasma and tissue-bound semicarbazide-sensitive amine oxidases (SSAOs) has been recognised for a long time, the physiological relevance of these enzymes still remains uncertain. The ability of SSAO to metabolise various aliphatic and aromatic monoamines differs between species, which limits the predictive value of the animal studies for human tissues. SSAO plays a protective role because the oxidative deamination of monoamines reduces their pharmacological activities. However, the products of deamination may be toxic. Several observations indicated that the plasma and tissue SSAO activities differ in certain disease states. It is proposed that selective inhibitors, of low toxicity, might be protective, through inhibiting the formation of the toxic products and the countering the disease-related elevation of SSAO activity. We reported earlier that there was a significant correlation between the serum SSAO activity and severity of atherosclerosis, as well as the intima-media thickness and serum cholesterol levels. Thus SSAO activity might be a clinical marker in the prognostic evaluation of diabetic-vascular complications. Although molecular biological studies are providing more and more reliable knowledge about the enzyme structure, many more studies should be carried out in different disease states are necessary to discover the clinical meaning of the enzyme function.