A microassay for the determination of monoamine oxidase activity using electron capture gas chromatography

Colorimetric assay for monoamine oxidase in tissues using peroxidase and 2,2'-azinodi(3-ethylbenzthiazoline-6-sulfonic acid) as chromogen

Monoamine oxidase is assayed in tissue by a colorimetric reaction using horse radish peroxidase and 2,2'-azinodi(ethylbenzthiazoline-6-sulfonic acid to measure H2O2 formed during oxidation of amines. The method has a coefficient of variation of approximately 2.5% and provides results comparable with those of radiometric assay. Monoamine oxidase activities in rat liver mitochondria and crude mitochondrial fraction from brain and with tyramine as a substrate were 18.9 +/- 0.4 and 4.61 +/- 0.15 nmol/min/mg of protein, respectively, using this method. Kinetic parameters of liver and brain monoamine oxidase with various substrates and inhibitors appeared to be the same when determined by either colorimetric or radiometric methods.

Assay for monoamine oxidases A and B by high-performance liquid chromatography with fluorescence detection

A sensitive method for the assay of monoamine oxidases A and B is described which employs high-performance liquid chromatography with fluorescence detection. Rat brain mitochondria were used as a preparation of the enzymes. p-Sulfamoylbenzaldehyde and benzaldehyde formed enzymatically from p-sulfamoylbenzylamine (the substrate of monoamine oxidase A) and benzylamine (the substrate of monoamine oxidase B), respectively, are converted simultaneously into fluorescent compounds with 2,2'-dithiobis(1-aminonaphthalene). These compounds are separated by reversed-phase chromatography on mu Bondapak CN. The limits of detection for p-sulfamoylbenzaldehyde and benzaldehyde formed enzymatically are 30 and 10 pmol per assay tube, respectively.