Abstract
Effects of some glycols on MAO in beef liver mitochondria were investigated and the following results were obtained.
(1) Addition of 10 %, 20% and 30% ethylene glycol caused increase of MAO activities in beef liver mitochondria by 35 %, 40% and 35 %, respectively. However, polyethylene glycol at concentrations of 0.1 %-20 % showed no effect on MAO activity. On the other hand, propylene glycol at concentrations of 10% and 20% showed marked inhibition of MAO activity by 20% and 30 %, respectively.
(2) This activating effect of MAO by ethylene glycol was also observed in the case of MAO in beef liver homogenate and of MAO solubilized from mitochondria. The same effects were also observed when tyramine, butylamine, β-phenylethylamine, benzylamine, amylamine, tryptamine or serotonin was used as substrate. The activating effect of ethyleneglycol was found to be reversible.
(3) The Km value of MAO in beef liver mitochondria was found to be 2×10-2 M with tyramine as substrate. This Km value did not change by addition of ethylene glycol but Vmax value was increased almost two fold. Moreover, the pH optima of MAO in beef liver mitochondria migrated from 7.0 to 7.5 and inhibition caused by excess of substrate was observed by addition of 10 % ethylene glycol in the reaction mixture.
