Hydrolysis of phosphatidylinositol 3,4-bisphosphate by inositol polyphosphate 4-phosphatase isolated by affinity elution chromatography.
Inositol polyphosphate 4-phosphatase is a monomeric 110-kDa protein that hydrolyzes two substrates in the inositol phosphate pathway. Inositol 3,4-bisphosphate is converted to inositol 3-phosphate, and inositol 1,3,4-trisphosphate is converted to inositol 1,3-bisphosphate. We have exploited the fact that inositol hexasulfate inhibits the enzyme to devise an affinity elution scheme from a Mono S cation exchange column that resulted in an 11,300-fold purified preparation of rat brain 4-phosphatase. The resulting 4-phosphatase hydrolyzed phosphatidylinositol 3,4-bisphosphate to phosphatidylinositol 3-phosphate with a first order rate constant 120-fold greater than that for inositol 3,4-bisphosphate and 900-fold greater than that for inositol 1,3,4-trisphosphate. This is now the third example wherein the same enzyme hydrolyzes both an inositol lipid and its analogous inositol phosphate.
Norris
F A
FA
Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
Majerus
P W
PW
D000818:Animals; D001921:Brain / Q000201:enzymology; D002846:Chromatography, Affinity; D006358:Hot Temperature; D007700:Kinetics; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D011489:Protein Denaturation; D051381:Rats
D018129:Phosphatidylinositol Phosphates; C060980:phosphatidylinositol 3,4-diphosphate; D010744:Phosphoric Monoester Hydrolases; C053153:phosphatidylinositol-3,4-bisphosphate 4-phosphatase