Abstract
A study of monoamine oxidase (MAO) has been made on homogenate of adult dog thoracic aorta and some characteristic properties of MAO in dog aorta were compared to that of MAO in dog serum and of MAO in dog liver.
The pH-activity curve of MAO in dog aorta showed a typical bell shape and its optimum pH was found to be 7.5 when MAO activity was measured by a slight modification of McEwen and Cohen's benzylamine method.
The maximum activity in pS-activity curve of dog aorta MAO was obtained at the concentration of 0.1 mM of benzylamine as substrate and it was found this value to be very low when compared to that of 10 mM obtained from dog liver MAO. The MAO in dog aorta and in dog serum were inhibited by KCN while MAO in dog liver was not inhibited at all.
Pargyline did not inhibited both MAO in dog aorta and in dog serum but strongly inhibited MAO in liver. Tris (hydroxymethyl) aminomethane showed strong inhibition against MAO in dog serum but did not show any effect on MAO in dog aorta and in dog liver. Moreover, marsilid and catron inhibited all three of MAO in dog serum, aorta and liver. From these results, it was suggested that MAO in dog aorta was a different enzyme from MAO in serum and in liver.
