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Catalytic domain of Type III Phosphoinositide 4-kinase PI4Ks catalyze the transfer of the gamma-phosphoryl group from ATP to the 4-hydroxyl of the inositol ring of D-myo-phosphatidylinositol (PtdIns) to generate PtdIns(4)P, the major precursor in the synthesis of other phosphoinositides including PtdIns(4,5)P2, PtdIns(3,4)P2, and PtdIns(3,4,5)P3. There are two types of PI4Ks, types II and III. Type II PI4Ks lack the characteristic catalytic kinase domain present in PI3Ks and type III PI4Ks, and are excluded from this family. Two isoforms of type III PI4K, alpha and beta, exist in most eukaryotes. The PI4K catalytic domain family is part of a larger superfamily that includes the catalytic domains of other kinases such as the typical serine/threonine/tyrosine protein kinases (PKs), aminoglycoside phosphotransferase, choline kinase, and RIO kinases.
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