GTP-dependent hydrolysis of phosphatidylinositol-4,5-bisphosphate by a soluble phospholipase C from adult human epidermis
The effects of tumor promoting phorbol esters, which activate protein kinase (C (PK-C), on epidermis suggest that PK-C is important in the regulation of epidermal growth and differentiation. Since in vivo PK-C is activated by the products of phospholipase C (PL-C)-catalyzed hydrolysis of phosphatidylinositol-4,5-bisphosphate (PIP/sub 2/), they have investigated the properties of this reaction. Soluble PL-C from adult human epidermis was incubated with sonicated lipid vesicles containing (/sup 3/H-inositol)PIP/sub 2/, for 10 minutes at 37/sup 0/C. Water soluble reaction products were extracted, chromatographed and quantitated. In the presence of physiological concentrations of Ca/sup + +/ magnesium and GTP PIP/sub 2/, but not phosphatidylinositol, was hydrolyzed by PL-C (11.7 nmol/min/mg). Addition of GTP or GTP..gamma..S stimulated activity greater than 15 fold. Half maximal and maximal activity were observed at 10 ..mu..M and 100 ..mu..M GTP..gamma..S, respectively. ATP was unable to substitute for GTP, and GDP/S inhibited PIP/sub 2/ hydrolysis in a dose dependent manner. Activity was sensitive to pH, and exhibited a sharp optimum at pH 6.5. In addition, the PL-C preparation specifically bound (/sup 35/S)GTP S. These data demonstrate that adult human epidermis contains PL-C activity that specifically hydrolyzes PIP/sub 2/ and suggest the involvement of a GTP-binding regulatory protein in this reaction.
- Research Organization:
- Univ. of Michigan Medical School, Ann Arbor
- OSTI ID:
- 5903182
- Report Number(s):
- CONF-870644-; TRN: 87-037310
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 46:6; Conference: 78. annual meeting of the American Society of Biological Chemists conference, Philadelphia, PA, USA, 7 Jun 1987
- Country of Publication:
- United States
- Language:
- English
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EPIDERMIS
CELL DIFFERENTIATION
LIPASE
ENZYME ACTIVITY
PHOSPHOLIPIDS
METABOLISM
CHROMATOGRAPHY
INHIBITION
MAN
NUCLEOTIDES
PROTEINS
SULFUR 35
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ANIMAL TISSUES
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CARBOXYLESTERASES
DAYS LIVING RADIOISOTOPES
ENZYMES
EPITHELIUM
ESTERASES
ESTERS
EVEN-ODD NUCLEI
HYDROLASES
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
LIPIDS
MAMMALS
NUCLEI
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
ORGANS
PRIMATES
RADIOISOTOPES
SEPARATION PROCESSES
SKIN
SULFUR ISOTOPES
TISSUES
VERTEBRATES
550501* - Metabolism- Tracer Techniques