Biosynthesis and localization of phosphatidyl-scyllo-inositol in barley aleurone cells.
A novel isomer of phosphatidylinositol (PI), phosphatidyl-scyllo-inositol, was characterized in the aleurone cells of barley seeds. In this investigation, the subcellular localization of scyllo-PI and the relative rates of biosynthesis and accumulation of [32P]phosphoric acid ([32Pi])-labeled scyllo- and myo-phosphoinositides in the plasma membrane and intracellular membrane pools were investigated. About 25% of the [32Pi]-labeled phospholipids were present in plasma membrane and 75% in intracellular membranes. Incorporation of [32Pi] into scyllo-PI was greater than into myo-PI in both the plasma membranes and intracellular membranes at all time points investigated, thus suggesting a higher rate of biosynthesis; however, the data do not preclude reduced breakdown of labeled scyllo-PI as a contributing factor. In vitro studies were conducted to investigate the presence of cytidinediphosphate diacylglycerol (CDP-DG):scyllo-inositol 3-phosphatidyltransferase (scyllo-PI synthase) and to optimize enzymatic activity. The inclusion of nonionic detergents (Brij 58 and Triton X-100) effected significant enhancement in the biosynthesis of scyllo-PI, whereas anionic, cationic, and zwitterionic detergents had little or no effect. This is the first evidence for CDP-DG:scyllo-inositol 3-phosphatidyltransferase activity.
Carstensen
S
S
Department of Chemistry, Michigan Technological University, Houghton 49931, USA.
Pliska-Matyshak
G
G
Bhuvarahamurthy
N
N
Robbins
K M
KM
Murthy
P P
PP
D051607:CDP-Diacylglycerol-Inositol 3-Phosphatidyltransferase; D002462:Cell Membrane / Q000378:metabolism; D003565:Cytidine Diphosphate / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D004075:Diglycerides / Q000378:metabolism; D001467:Hordeum / Q000166:cytology / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism; D007536:Isomerism; D010716:Phosphatidylinositols / Q000032:analysis* / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D010761:Phosphorus Radioisotopes / Q000378:metabolism; D012639:Seeds / Q000166:cytology / Q000378:metabolism; D015398:Signal Transduction; D017855:Transferases (Other Substituted Phosphate Groups) / Q000187:drug effects / Q000378:metabolism; D014316:Tritium
D003902:Detergents; D004075:Diglycerides; D010716:Phosphatidylinositols; D010761:Phosphorus Radioisotopes; D014316:Tritium; D003565:Cytidine Diphosphate; D017855:Transferases (Other Substituted Phosphate Groups); D051607:CDP-Diacylglycerol-Inositol 3-Phosphatidyltransferase