Nature of Phosphatase Activity

Abstract

CLOETENS¹, after a careful investigation of the reactivation of dialysed alkaline intestinal phosphatase, concluded that alkaline phosphatases in general consist of a slightly active or completely inactive part and the two ions, magnesium and zinc. The observations of Hove, Elvehjem and Hart², and of Thoai, Roche and Roger³, showed the importance of certain amino-acids in restoring activity when particular inorganic ions were also present. Thus, it was evident that the dialysable prosthetic group may be a combination of compounds containing these amino-acids with a metal other than magnesium, possibly zinc. But Abul-Fadl and King⁴, in their experiments on kidney alkaline phosphatase, observed that the three main factors which were important for the activity of this enzyme were a specific protein, a specific dialysable organic group or groups not of the nature of an amino-acid, and an inorganic ion, magnesium. They stated that the two-metal theory of Cloetens was highly improbable, since no evidence of the indispensability of zinc was obtained.