Serine base exchange enzyme activity is modulated by sphingosine and other amphiphilic compounds: possible role of positive charge in increasing the synthesis of phosphatidylserine.
It has been found that sphingosine and sphingosylphosphorylcholine (amphiphilic cations) have a stimulatory, and cholesterol 3-sulfate (an amphiphilic anion), an inhibitory, effect on [14C]serine incorporation into phosphatidylserine in glioma C6 and rat liver microsomes. In glioma intact cells sphingosine stimulates phosphatidylserine synthesis in a process independent of protein kinase C, but suppressed by thapsigargin. We suggest that the stimulation of the enzyme occurs by the interaction of amphiphilic cations with the membrane cosubstrate phospholipids, leading to a charge redistribution on their phosphate groups, and hence facilitating the enzyme action. A new hypothesis concerning the mechanism of the serine base exchange reaction is discussed.
Wiktorek-Wójcik
M
M
Department of Molecular and Cellular Neurobiology, Nencki Institute of Experimental Biology, 3 Pasteur Street, Warsaw, 02-093, Poland.
Banasiak
M
M
Czarny
M
M
Stepkowski
D
D
Barańska
J
J
D000818:Animals; D002788:Cholesterol Esters / Q000494:pharmacology; D005910:Glioma / Q000201:enzymology*; D007700:Kinetics; D008861:Microsomes / Q000201:enzymology*; D008862:Microsomes, Liver / Q000201:enzymology*; D019884:Nitrogenous Group Transferases / Q000378:metabolism*; D010718:Phosphatidylserines / Q000096:biosynthesis*; D010767:Phosphorylcholine / Q000031:analogs & derivatives / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D002788:Cholesterol Esters; D010718:Phosphatidylserines; C005356:sphingosine phosphorylcholine; D010767:Phosphorylcholine; D019284:Thapsigargin; D019884:Nitrogenous Group Transferases; D011493:Protein Kinase C; C022370:phospholipid serine base exchange enzyme; C007045:cholesteryl sulfate; D013110:Sphingosine; D013755:Tetradecanoylphorbol Acetate