Phosphatidylinositol-specific phospholipase C activity of chromaffin granule-binding proteins

Journal Article · Tue Jun 25 04:00:00 EDT 1985 · J. Biol. Chem.; (United States)

OSTI ID:6380929

Creutz, C E; Dowling, L G; Kyger, E M; Franson, R C

Using (U-/sup 14/C)phosphatidylinositol as substrate, Ca/sup 2 +/-dependent phospholipase C activity was detected in a group of bovine adrenal medullary proteins that bind to chromaffin granule membranes in the presence of Ca/sup 2 +/. The activity was maximal at neutral pH and represented an 80- to 240-fold enrichment of adrenal medullary cytosol phospholipase C activity measured at pH 7.3. The stimulation of activity by Ca/sup 2 +/ was complex; no activity was present in the absence of Ca/sup 2 +/, 25% activation occurred at 1 microM Ca/sup 2 +/, and full activation at 5 mM Ca/sup 2 +/. The enzyme bound to chromaffin granule membranes in the presence of 2 mM Ca/sup 2 +/ but was released at 40 microM Ca/sup 2 +/, suggesting that intrinsic enzyme activity may be regulated by (Ca/sup 2 +/) at 1 microM, but additional activation at higher concentrations of Ca/sup 2 +/ is seen in vitro as a result of Ca/sup 2 +/-dependent binding of the active enzyme to substrate-containing membranes. This enzyme may generate diacylglycerol and phosphorylated inositol to act as intracellular messengers in the vicinity of the chromaffin granule membrane during the process of exocytosis.

• OSTI ID: 6380929
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 12; ISSN JBCHA
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH METALS
ANIMALS
BIOCHEMICAL REACTION KINETICS
CALCIUM
CARBOHYDRATES
CARBON 14 COMPOUNDS
CARBOXYLESTERASES
CATIONS
CATTLE
CELL CONSTITUENTS
CELL MEMBRANES
CHARGED PARTICLES
DOMESTIC ANIMALS
ELEMENTS
ENZYME ACTIVITY
ENZYMES
ESTERASES
HYDROLASES
INOSITOL
INOSITOLS
IONS
KINETICS
LABELLED COMPOUNDS
LIPASE
MAMMALS
MEMBRANES
METALS
MONOSACCHARIDES
ORGANIC COMPOUNDS
PROTEINS
REACTION KINETICS
RUMINANTS
SACCHARIDES
VERTEBRATES