MONO-AMINE OXIDASE FROM BEEF-LIVER MITOCHONDRIA - SIMPLIFIED ISOLATION PROCEDURE, PROPERTIES, AND DETERMINATION OF ITS CYSTEINYL FLAVIN CONTENT

A novel procedure is described for the isolation of monoamine oxidase from beef liver mitochondria. The procedure involves extraction of inert protein after simultaneous digestion with phospholipases A and C, followed by extraction of the enzyme by a low concentration of Triton X-100 and polymer partition. The specific activity equals the best value in the literature, but the yield is several times higher than in published procedures. On the basis of the flavin content the molecular weight is 146,000. Gel electrophoresis in the presence of sodium dodecyl sulfate and mercaptoethanol yields a single band of 62,000 molecular weight. Thus, it appears that the native enzyme contains two subunits not separable on polyacrylamide gels, only one of which possesses covalently linked flavin. A procedure is also described for the determination of the cysteinyl flavin content of purified preparations of the enzyme. © 1979.