Evaluation of the assay for serum monoamine oxidase -- an index of hepatic fibrosis.
At present, neither the diagnostic efficiency, the analytic reliability nor the practicability of clinical chemical tests for estimation of the degree and/or activity of the fibrotic transformation of the chronically injured liver are satisfactory. Among the various parameters proposed, the determination of the activity of monoamine oxidase (monoamine: O2 oxidoreductase, EC 1.4.3.4) in serum seems to be advantageous. To facilitate its routine use we studied some important practical aspects of the new colorimetric assay for the activity of monoamine oxidase in serum. The reaction proceeds linearly with time for at least two hours and with enzyme concentrations up to kU/l. The buffer composition influences markedly the function of the enzyme; in Tris-HCl buffer (pH 7.2) at 37 degree C the activity is 1.35 time higher than in phosphate buffer (pH 7.3) and the temperature correlation factors are also different for both buffer systems. 0.003 mol/l of the lathyrogenic compound beta-aminopropionitrile inhibits the activity by about 50% whereas Cu2+ up to 130 mu mol/l does not affect enzyme function. Intra- and interassay precision and characterized by a CV of 3.6 and 12%, respectively. Hemolysis and hyperbilirubinemia do not interfere significantly with the determination but in hyperlipemic sera elevated enzyme activities were noticed. During storage of serum at room temperature the catalytic function decrease by about 30%/day. Of the 26 quality control sera tested, only a few contained monoamine oxidase activity that was quantitatively (i.e. similar catalytic activity in tris phosphate buffer) similar to that in human serum, and were therefore suitable for routine precision control analysis.
D000629:Aminopropionitrile / Q000494:pharmacology; D006454:Hemoglobins / Q000378:metabolism; D006461:Hemolysis; D006801:Humans; D006932:Hyperbilirubinemia / Q000201:enzymology; D008107:Liver Diseases / Q000201:enzymology*; D008995:Monoamine Oxidase / Q000097:blood*; D013696:Temperature
D006454:Hemoglobins; D000629:Aminopropionitrile; D008995:Monoamine Oxidase