Immobilization of Acid Phosphatase and Its Use for Dephosphorylation of Casein

Abstract

Wheat germ phosphatase (WP), sweet potato phosphatase (SP) and bovine spleen phospho-protein phosphatase (BP) were immobilized on aminoalkylsilyl glass beads with glutaraldehyde, and denoted as IWP, ISP and IBP, respectively. Their activity yields were in the range of 16 ~ 44%. By this immobilization, the pH optima for WP and SP shifted one pH unit to the acid side and the temperature optima did not change. Their stabilities regarding pH and temperature were also comparable but their Km values were visibly increased compared with enzymes in the soluble state. The immobilized acid phosphatases were able to be used for limited hydrolysis of the phosphoryl group in casein. Rennet curd, with a smaller tension value, was obtained using test-milk dephosphorylated with IWP or ISP. The addition of CaCl₂ was found to slow down the phosphorylation of casein.