The alkaline phosphomonoesterase is a magnesium-apoenzyme complex. In the dialyzed swine kidney autolysate, magnesium, zinc, manganese, calcium and iron were found but no copper.
A slight hydrolytic action, even without the addition of magnesium, is due to this ion present in the autolysate itself. Its concentration was calculated to be 4.8×10-6M in the hydrolyzing test solution through analysis of the activity curve and the value agreed approximately with that obtained by colorimetric analysis of the dialyzed autolysate.
Zinc ion is inhibitory to apoenzyme by competition with magnesium. Some chelating reagents, for instance, ethylenediamine capable of complex formation with zinc could slightly activate the enzyme of the dialyzed autolysate.
Polarographic estimation of zinc concentration in the autolysate revealed it to be 3.8×10-7M. This value nearly agreed with 6.9×10-7M, calculated from the point of competition with magnesium.
Manganese salt was effective for activation of enzyme at lower concentrations than magnesium. However, at its higher concentration an inhibition took place because of formation of inactive complex with the second manganese ion. The result of manganese analysis in the autolysate showed that the concentration of manganese in the test solution was so low that any activation of the enzyme could not take place.
The inhibition by copper was non-competitive with magnesium.
The author wishes to express his sincere thanks to Prof. S. Akamatsu for his kind guidance in this work. This investigation was supported by a Grant in Aid for Scientific Research from the Ministry of Education to Prof. S. Akamatsu.
