Some properties of alkaline phosphatase of cow's milk and calf intestinal mucosa

Abstract

The properties of purified al- kaline phosphatases from cows milk and calf intestinal mucosa were studied. Chemical analyses show that both enzymes are colorless un-conjugated proteins, substantially free of organic P, and of nucleotides or related compounds. They may contain small amounts of carbohydrate. The tyrosine and tryptophan contents are very similar. The 2 enzymes differ in their activity/pH relationships. The influence of Mg, Mn, Ca, Zn and Be on the activities of the 2 enzymes were investigated, using both crude and purified enzyme preparations. Maximum activity of the purified enzymes is obtained with MgCl2 (10-2 [image]). Be and Zn salts both cause considerable inhibitions. Pre-incubation of the purified enzymes with alanine and Mg causes no greater activity than that obtained using magnesium acetate alone without any pre-incubation. Alanine protects the enzyme under certain treatments. The effects observed with alanine and other amino acids is discussed in relation to the experimental procedures used by various workers. No evidence was obtained to support claims for the existence of dissociable organic "coenzymes" of alkaline phosphatases. Evidence is presented that the milk and intestinal enzymes are distinctly different, although they have similar specificities.