Identification of rat liver phosphatidylinositol synthase as a 21 kDa protein.
Substantial purification of rat liver phosphatidylinositol (PtdIns) synthase has been achieved by a combination of Hecameg extraction, heat treatment, affinity chromatography and chromatography on PBE-94. The activity chromatographs as a single peak which has an apparent molecular mass between 150 and 200 kDa on Sepharose 4B. When analysed by SDS/PAGE, two major bands are seen. The enzyme activity is correlated with a protein band of 21 kDa. A second band, at 51 kDa, is eluted from a PBE-94 column slightly ahead of the activity. Manganese is an absolute requirement for stabilization of activity in the presence of detergent. The effect of manganese is optimal at 0.5 mM; magnesium at a concentration of 10 mM is only minimally effective. Substrate Kms are 1.3 mM and 9.5 microM for inositol and CDP-diacylglycerol respectively. The activity eluting from the PBE-94 column is purified 5000-fold over the post-mitochondrial supernatant.
Monaco
M E
ME
Department of Physiology, New York University Medical Center, NY 10010.
Feldman
M
M
Kleinberg
D L
DL
D000818:Animals; D051607:CDP-Diacylglycerol-Inositol 3-Phosphatidyltransferase; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D008099:Liver / Q000201:enzymology*; D008565:Membrane Proteins; D008970:Molecular Weight; D051381:Rats; D017855:Transferases (Other Substituted Phosphate Groups) / Q000302:isolation & purification*
D008565:Membrane Proteins; D017855:Transferases (Other Substituted Phosphate Groups); D051607:CDP-Diacylglycerol-Inositol 3-Phosphatidyltransferase; C496767:Cdipt protein, rat