The catalytic-centre activity and kinetic properties of bovine milk alkaline phosphatase

Abstract

The phosphorylation of milk alkaline phosphatase was studied under various conditions: maximum incorporation occurred at pH 5.0 and 50% incorporation at pH 6.6-7.0. The phosphorylation was shown to be specific and the results suggest that the active center ot the enzyme is involved in the process. Phosphoryl-enzyme is rapidly hydrolyzed at alkaline pH. At pH 7.0 the results suggest that a phosphoryl-enzyme could occur as a transient intermediate in the hydrolysis of phosphate esters by the phosphatase. The catalytic-center activity of the enzyme was found to be 2700 sec.-l at pH 10.0 and 25[degree] with p-nitrophenyl phosphate as substrate.