Two distinct membrane-bound phosphatidylinositol-4-phosphate phosphatases in bovine brain.
Solubilized phosphatidylinositol-4-phosphate 4-phosphatase from bovine brain resolved into two peaks of activity by ion exchange chromatography. Both exhibited substantial detergent binding characteristic of integral membrane proteins, and both appear specific for phosphatidylinositol-4-phosphate, but their pH optima differ: the earlier eluting fraction (peak 1) is optimally active between pH 5.5 and 6, whereas the later eluting fraction (peak 2) is most active around pH 8.5. Detergent inhibition studies suggest that peak 2, but not peak 1, interacts with phosphatidylinositol-4-phosphate in the context of a single mixed micelle. Further characterization of these activities should help shed light on the biological function of polyphosphoinositide phosphatases.
Wang
S M
SM
Department of Biochemistry, University of Alabama, Birmingham 35294-0005.
Ganong
B R
BR
D000818:Animals; D001921:Brain / Q000201:enzymology*; D002417:Cattle; D002499:Centrifugation, Density Gradient; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D010744:Phosphoric Monoester Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D010761:Phosphorus Radioisotopes
D007527:Isoenzymes; D010761:Phosphorus Radioisotopes; D010744:Phosphoric Monoester Hydrolases; C053153:phosphatidylinositol-3,4-bisphosphate 4-phosphatase