Identification, purification and characterization of a novel phosphatidylinositol‐specific phospholipase C, a third member of the β subfamily

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Abstract
The partial sequence of a novel PtdIns‐specific phospholipase C of the β subfamily (PtdIns‐PLCβ3) is described. Based upon the predicted protein sequence, monospecific antibodies have been raised and used to identify a suitable source for purification of the protein. Fractionation of HeLa S3 cells revealed that immunoreactive PtdIns‐PLCβ3 is membrane associated; purification (∼1000‐fold) from this fraction yielded a single immunoreactive protein of 158 kDa, with a specific activity of 136 μmol · min−1· mg−1, with PtdIns 4,5‐bisphosphate as substrate. Substrate specificity and Ca2+ dependence of this purified PtdIns‐PLC are characteristic of the PtdIns‐PLCβ subfamily.