A water-soluble analogue of glucosaminylphosphatidylinositol distinguishes two activities that palmitoylate inositol on GPI anchors.
2-Palmitoylation of the inositol residue occurs during biosynthesis of glycosylphosphatidylinositol (GPI) anchors, but the enzymology of this step has been enigmatic. With endogenously synthesized glucosamine-PI (GlcN-PI; a GPI intermediate), a CoA-dependent palmitoyl-CoA-independent acyltransfer activity (AT-1) has been reported in rodent preparations. In contrast, a palmitoyl-CoA-dependent GlcN-PI acyltransferase activity (AT-2) was reported in both rodent and yeast preparations with a novel water-soluble dioctanoyl GlcN-PI analogue, GlcN-PI(C8). We report that AT-1, as well as AT-2, can be detected in rodent microsomes with GlcN-PI(C8), thus demonstrating the coexistence of these activities in a single membrane preparation and the general utility of GlcN-PI(C8) for studying the GPI pathway. Unexpectedly, AT-2 was peripherally associated with microsomes, a property atypical for GPI biosynthetic enzymes.
Doerrler
W T
WT
Cell Regulation Graduate Program, Department of Pharmacology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas, 75390-9041, USA.
Lehrman
M A
MA
D000217:Acyltransferases / Q000378:metabolism; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D006155:Guanosine Diphosphate Mannose / Q000378:metabolism; D007425:Intracellular Membranes / Q000201:enzymology; D008861:Microsomes / Q000201:enzymology*; D008956:Models, Chemical; D019308:Palmitic Acid / Q000378:metabolism*; D010171:Palmitoyl Coenzyme A / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism*
D017261:Glycosylphosphatidylinositols; D010716:Phosphatidylinositols; D010171:Palmitoyl Coenzyme A; D019308:Palmitic Acid; D006155:Guanosine Diphosphate Mannose; D000217:Acyltransferases