Purification and solubilization of monoamine oxidase of rat liver mitochondria

Monoamine oxidase in adult Ascaridia galli

Monoamine oxidase (MAO), catalysing oxidative deamination of biogenic monoamines, has been detected in adult Ascaridia galli. MAO was present in mitochondria and deaminated noradrenaline at the maximal rate, although serotonin, adrenaline, tyramine and dopamine were also degraded but more slowly. Of the organs studied, the body wall, female reproductive organ and intestine, the body wall (containing neuronal structures) showed highest MAO activity. Km value for chick ascarid mitochondrial MAO using tyramine as substrate was 1.66 X 10(-3) M and it was most active at 2.5 mM tyramine concentration, pH 7.5 and 40 degrees C. MAO of A. galli appeared to be thermolabile as nearly 80% of its activity was lost when the incubation temperature was increased 5 degrees above optimum.

Localization, purification and substrate specificity of monoamine oxidase

Bovine kidney monoamine oxidase (amine:oxygen oxidoreductase (deaminating) (flavin-containing), EC 1.4.3.4) has been purified to one band on disc electrophoresis, and is shown to be localized in the intra- and extramitochondrial membrane. Kinetic models have been used to determine the effect of different substances on the enzyme activity. This enzyme shows a very high substrate specificity. It is suggested that phenol ring and one hydrogen atom each on the methylene and amine groups are responsible for the enzyme activity. N-methylbenzylamine exhibits a homotropic negative cooperative effect which is also supported by the n and Rs values. Benzylhydrazine is apparently a good substrate unlike phenylhydrazine, semicarbazide, harmaline and alpha- and beta-naphthol which show an inhibitory effect on the enzyme activity. Methylamine has no effect. It is suggested that the enzyme may have different sites or different conformations for different substrates. The results of this communication demonstrate bovine kidney monoamine oxidase to be different from monoamine oxidase from other sources.

Brain monoamine oxidase in mice after exposure to aggression and defeat

Effects on the monoamine Oxidase activity of the hypothalamus, amygdala, and frontal cortex of untrained mice exposed to repeated defeat by trained fighters for two 5-minute periods a day for 0, 1, 2, 4, 8, 14, or 20 days were studied. Activity in the hypothalamus increased significantly during the first 2 days of fighting, while the activity in the amygdala and frontal cortex remained essentially unchanged. After 8 days, activity in all three brain areas declined. After 14 days of fighting the monoamine Oxidase activity returned to normal, but another decrease was observed in the three areas after 20 days of fighting.