Phosphatidylinositol 4,5-bisphosphate phospholipase C and phosphomonoesterase in Dunaliella salina membranes

• Published in: Plant physiology (Bethesda) Vol. 90; no. 3; pp. 1115 - 1120
• Main Authors: Einspahr, K.J. (University of Texas, Austin, TX), Peeler, T.C, Thompson, G.A. Jr
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01.07.1989
• Subjects: 550201 - Biochemistry- Tracer Techniques; ACTIVIDAD ENZIMATICA; ACTIVITE ENZYMATIQUE; ALGAE; ALGUE; ALKALINE EARTH METALS; BASIC BIOLOGICAL SCIENCES; biochemistry; Biological and medical sciences; CALCIO; CALCIUM; CARBOHYDRATES; CELL CONSTITUENTS; CELL MEMBRANES; Cell physiology; Cells, cell elements: structure and function; Chloroplasts; complex lipids; Dunaliella; Dunaliella salina; ELEMENTS; ENZIMAS; enzymatic activity; ENZYME; ENZYME ACTIVITY; ENZYMES; ESTERS; ESTRUCTURA CELULAR; FOSFATOS; FOSFOLIPIDOS; Freshwater; Fundamental and applied biological sciences. Psychology; HIDROGENO; HYDROGEN COMPOUNDS; HYDROGENE; HYDROLASES; INOSITOL; INOSITOLS; ION; IONES; ISOTOPE APPLICATIONS; LIPIDS; MEMBRANES; METALS; MONOSACCHARIDES; ORGANIC COMPOUNDS; ORGANIC PHOSPHORUS COMPOUNDS; PHOSPHATE; Phosphates; PHOSPHATIDE; phosphatidylinositol 4,5-bisphosphate phospholipase C; phosphatidylinositol 4,5-bisphosphate phosphomonoesterase; Phosphatidylinositols; PHOSPHOLIPIDS; Plant cells; Plant physiology and development; PLANTS; plasma membranes; PLASTE; PLASTIDIOS; SACCHARIDES; Signal transduction; STRUCTURE CELLULAIRE; TECHNIQUE DES TRACEURS; TECNICAS DE AISLAMIENTO DE ISOTOPOS; TRACER TECHNIQUES; TRITIUM COMPOUNDS; Cell culture; Radiolabelling; Algae; Chlorophycophyta; In vitro; Phospholipase C; Dunaliella salina; Enzymatic activity; Investigation method; Membrane fraction; Plasma membrane; Localization; Thallophyta
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.90.3.1115

In comparison with other cell organelles, the Dunaliella salina plasma membrane was found to be highly enriched in phospholipase C activity toward exogenous [3H]phosphatidylinositol 4,5-bisphosphate (PIP2). Based on release of [3H]inositol phosphates, the plasma membrane exhibited a PIP2-phospholipase C activity nearly tenfold higher than the nonplasmalemmal, nonchloroplast 'bottom phase' (BP) membrane fraction and 47 times higher than the chloroplast membrane fraction. The majority of phospholipase activity was clearly of a phospholipase C nature since over 80% of [3H]inositol phosphates released were recovered as [3H]inositol trisphosphate (IP3). These results suggest a plausible mechanism for the rapid breakdown of PIP2 and phosphatidylinositol 4-phosphate (PIP) following hypoosmotic shock. Quantitative analysis of major [3H]inositol phospholipids during these assays revealed that some of the [3H]-PIP2 was converted to [3H]phosphatidylinositol 4-monophosphate (PIP) and to [3H]phosphatidylinositol (PI) in the BP fraction of membrane remaining after removal of plasmalemma and chloroplasts. This latter fraction is enriched more than fivefold in PIP2/PIP phosphomonoesterase activity when compared to the plasmalemma or chloroplast membrane fractions. We have also examined some of the in vitro characteristics of the plasma membrane phospholipase C activity and have found it to be calcium sensitive, reaching maximal activity at 10 micromolar free [Ca2+]. We also report here that 100 micromolar GTP gamma S stimulates phosphospholipase C activity over a range of free [Ca2+]. Together, these results provide evidence that the plasma membrane PIP2-phospholipase C of D. salina may be subject to Ca2+ and G-protein regulation