Abstract
The difference between the enzymic properties of bovine serum and liver MAO and the effects of several reagents on these enzymes were studied, measuring activity manometrically at 38°C. Serum MAO oxidized benzylamine rapidly, but did not oxidize tryptamine or serotonin. Liver MAO showed highest activity with tyramine, but also oxidized various other monoamines. The pS maxima of serum MAO and liver MAO were 10 mM and 30 mM and their pH optima were 7.0 and 8.1, respectively. Addition of sodium nitrite (NaNO2) or potassium nitrite (KNO2) stimulated liver MAO, activity increasing with increase in the concentrations of these reagents. On the contrary, the activity of serum MAO decreased with increase in the concentrations of these reagents. Hydroxyla-mine (NH2OH) completely inhibited the activities of serum MAO and liver MAO at concentrations of 0.1 mM and 0.1 M, respectively. The effects of these reagents on the pS maxima and pH optima of serum MAO and liver MAO were different. The Km value of serum MAO for benzylamine was 1.6 mM and NaNO2, KNO2 and NH2OH caused noncompetitive inhibition.
