Phosphatidylcholine enhances the activity of rat liver type II phosphatidylinositol-kinase.
A PtdIns 4-kinase was purified extensively from rat liver exocytotic vesicles. The enzyme had a low Km for ATP, was inhibited by adenosine, and had an apparent molecular mass of 54 kDa, indicating it to be a type II PtdIns-kinase. The activity of the purified enzyme was enhanced several-fold by PtdCho, and to some extent by other phospholipids with basic polar head groups, and was inhibited by PtdSer. Kinetic analyses, presenting the substrate in mixed micelles of Triton X-100, PtdIns and PtdCho, showed that the effect of PtdCho was both to increase Vmax and to decrease the apparent Km for micellar PtdIns.
Biochemistry, Chemical Centre, University of Lund, Sweden.
H
H
Olsson
W
W
Martínez-Arias
B
B
Jergil
D019870:1-Phosphatidylinositol 4-Kinase; D000818:Animals; D002850:Chromatography, Gel; D004789:Enzyme Activation; D005089:Exocytosis; D008099:Liver / Q000201:enzymology*; D008823:Micelles; D010713:Phosphatidylcholines / Q000494:pharmacology*; D010743:Phospholipids / Q000494:pharmacology; D010770:Phosphotransferases / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats
D008823:Micelles; D010713:Phosphatidylcholines; D010743:Phospholipids; D010770:Phosphotransferases; D019870:1-Phosphatidylinositol 4-Kinase