Effects of okadaic acid on the activities of two distinct phosphatidate phosphohydrolases in rat hepatocytes.
Incubation of hepatocytes with okadaic acid displaced the N-ethylmaleimide-sensitive phosphatidate phosphohydrolase from the membrane fraction into the cytosol and partially prevented the oleate-induced movement of phosphohydrolase from cytosol to membranes. However, higher concentrations of oleate still caused translocation and activation of the phosphohydrolase. This enzyme is stimulated by Mg2+, and is probably involved in glycerolipid synthesis. Okadaic acid also decreased the concentration of diacylglycerol within the hepatocytes. Okadiac acid had no observable effect on the activity of an N-ethylmaleimide-insensitive phosphatidate phosphohydrolase which remained firmly attached to membranes. This activity is not stimulated by Mg2+ and is probably involved in signal transduction by the phospholipase D pathway.
Gomez-Muñoz
A
A
Department of Biochemistry, Faculty of Medicine, University of Alberta, Edmonton, Canada.
Hatch
G M
GM
Martin
A
A
Jamal
Z
Z
Vance
D E
DE
Brindley
D N
DN
D000818:Animals; D001692:Biological Transport; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D004988:Ethers, Cyclic / Q000494:pharmacology*; D005033:Ethylmaleimide / Q000494:pharmacology; D007527:Isoenzymes; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D019319:Okadaic Acid; D019301:Oleic Acid; D009829:Oleic Acids / Q000494:pharmacology; D010711:Phosphatidate Phosphatase / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013347:Subcellular Fractions / Q000201:enzymology
D004988:Ethers, Cyclic; D007527:Isoenzymes; D009829:Oleic Acids; D019319:Okadaic Acid; D019301:Oleic Acid; D010711:Phosphatidate Phosphatase; D008274:Magnesium; D005033:Ethylmaleimide