Effects of Cysteine and Acetic Anhydride on the Antigenic and Catalytic Sites of Dog Intestinal Alkaline Phosphatase¹

Treatment of alkaline phosphatase(s) from dog intestine with cysteine causes the complete destruction of its enzymatic activity without impairing its ability to combine with and be precipitated by its antiserum.

Treatment of the enzyme with acetic anhydride, although leaving its catalytic properties largely intact, destroys the ability of the enzyme to be precipitated by antiserum. However, combination with antibody, in the form of soluble complexes still takes place. These complexes are precipitated upon the addition of horse antirabbit γ-globulin antibodies.

The relation of these observations to the chemical nature of the catalytic and antigenic sites of alkaline phosphatase is discussed.