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Identification and characterization of a sac domain-containing phosphoinositide 5-phosphatase
T Minagawa1, T Ijuin, Y Mochizuki
1Department of Biochemistry, The Institute of Medical Science, University of Tokyo, Shirokanedai, Minato-ku, Tokyo 108-8639 Japan.
Abstract:
We have characterized a novel Sac domain-containing inositol phosphatase, hSac2. It was ubiquitously expressed but especially abundant in the brain, heart, skeletal muscle, and kidney. Unlike other Sac domain-containing proteins, hSac2 protein exhibited 5-phosphatase activity specific for phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol 3,4,5-trisphosphate. This is the first time that the Sac domain has been reported to possess 5-phosphatase activity. Its 5-phosphatase activity for phosphatidylinositol 4,5-bisphosphate (K(m) = 14.3 microm) was comparable with those of Type II 5-phosphatases. These results imply that hSac2 functions as an inositol polyphosphate 5-phosphatase.