Studies on alkaline phosphatase. Phosphorylation of calf intestinal alkaline phosphatase by 32P-labelled pyrophosphate |
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| Authors: | H. N. Fernley and Sylvia Bisaz |
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| Affiliation: | Department of Biochemistry, Institute of Orthopaedics, Stanmore, Middlesex, and Laboratorium für experimentelle Chirurgie, Schweizerisches Forschungsinstitut, Davos-Platz, Switzerland |
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| Abstract: | 1. A purified preparation of alkaline phosphatase from calf-intestinal mucosa was phosphorylated by (32)P-labelled PP(i) at a serine residue on the enzyme. Under the conditions employed, up to 0.15mum-labelled sites were obtained from 1mum-[(32)P]PP(i). 2. The phosphorylated enzyme was labile, the rate of dephosphorylation being similar to the overall rate of substrate hydrolysis. 3. A stopped-flow technique was used to determine the number of phosphomonoesterase active sites, which agreed with the number of (32)P-labelled sites. 4. It is concluded that calf-intestinal alkaline phosphatase is both a phosphomonoesterase and a pyrophosphatase. |
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