Topology and lipid protein association of MAO-A and MAO-B
Oxidative deamination of biogenic monoamines is believed to be accomplished by at least two principal functionally different forms of monoamine oxidase (MAO, EC 22.214.171.124) (Tipton, et al., 1976). In rat brain, serotonin is deaminated by MAO-A whereas phenylethyl amine is deaminated by MAO-B (Jain, 1977). The multiple MAO enzymes which have been localized in the outer mitochondrial membrane are intrinsic membrane-bound flavoproteins (Greenawalt and Schnaitman, 1970). Vigorous procedures involving sonication, organic solvent extraction, and/or detergent treatment are required to solubilize the enzyme with concomitant preferential loss of the MAO-A characteristics (Tipton, 1975). Treatment of the solubilized MAO active fractions with chaotropic agents to remove the lipid moiety results in the disappearance of the apparent multiplicity both in terms of electrophoretic mobility and substrate-inhibitor specificity (Houslay and Tipton, 1973). These results favor the model that the MAO-A and B activities reside with the same enzymic protein. However, immunochemical studies (Dennick and Mayer, 1977; McCauley and Racker, 1973) show equivocal results.
KeywordsMonoamine Oxidase Phosphatidic Acid Outer Mitochondrial Membrane Brain Mitochondrion Biogenic Monoamine
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