Abstract
The influence of temperatures of between 15°C and 45°C on mitochondrial monoamine oxidase (MAO) from rat liver was studied. Results showed that its activities with four substrates increased markedly with increase in temperature. Simple activity curves were obtained with benzylamine and β-phenylethylamine as substrates whereas a pair of sigmoid curves jointed by a horizontal region was obtained with serotonin and a mixed curve was obtained with tyramine. The effect of heat-treatment on the mitochondrial MAO activities with the four substrates were also studied. The activities toward serotonin and tyramine were fairly heat-stable, but those toward benzylamine and β-phenylethylamine were heatlabile. These results suggest that there may by two different forms or separate active sites in an active center of the enzyme in rat liver mitochondria.
