Parallel increase of dolichol pathway and nucleotide pyrophosphatases in rat hepatocytes by dexamethasone
Incorporation of (/sup 14/C)-mannose to dolichol phosphate mannose, dolichol pyrophosphate oligosaccharide and N-linked glycoproteins in cultured hepatocytes was increased by dexamethasone. Nucleotide pyrophosphatases are now measured to investigate possible control of glycosylation by the nucleotide sugar pools. Dexamethasone caused about 2 fold increase of UDP-GlcNAc and GDP-Man pyrophosphatase activity which is evident as early as 4 hr and increased up to 12 hr of incubation. The K/sub m/ for UDP-GlcNAc and GDP-Man were respectively 0.43 mM and 0.47 mM in homogenate membrane and the values remained unchanged by dexamethasone treatment. However the V/sub max/ of the enzymes were increased with both UDP-GlcNAc and GDP-Man. The broad pH optima of the enzymes (pH 8 to 10) indicated their alkaline nature. Mixing experiments of the cell homogenates from control and dexamethasone treated cells showed that UDP-GlcNAc and GDP-Man pyrophosphatase activities were additive which ruled out the possibility of presence of any activator or removal of any inhibitor due to dexamethasone. The parallel increase of nucleotide pyrophosphatase and dolichol linked pathway by dexamethasone does not support the possibility that stimulation of glycoprotein synthesis by dexamethasone is mediated by transfer of nucleotide sugars towards dolichol saccharides.
- Research Organization:
- Univ. of Newfoundland, St. John's
- OSTI ID:
- 7246479
- Report Number(s):
- CONF-8606151-; TRN: 86-039103
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 45:6; Conference: 76. annual meeting of the Federation of American Society for Experimental Biology, Washington, DC, USA, 8 Jun 1986
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
DEXAMETHASONE
BIOCHEMICAL REACTION KINETICS
MANNOSE
METABOLISM
PHOSPHATASES
ENZYME ACTIVITY
BIOLOGICAL PATHWAYS
CARBON 14 COMPOUNDS
CELL MEMBRANES
GLUCOPROTEINS
LIPIDS
LIVER CELLS
NUCLEOTIDES
OLIGOSACCHARIDES
RATS
TRACER TECHNIQUES
ADRENAL HORMONES
ALDEHYDES
ANIMAL CELLS
ANIMALS
CARBOHYDRATES
CELL CONSTITUENTS
CORTICOSTEROIDS
ENZYMES
ESTERASES
GLUCOCORTICOIDS
HEXOSES
HORMONES
HYDROLASES
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
KETONES
KINETICS
LABELLED COMPOUNDS
MAMMALS
MEMBRANES
MONOSACCHARIDES
ORGANIC COMPOUNDS
PREGNANES
PROTEINS
REACTION KINETICS
RODENTS
SACCHARIDES
SOMATIC CELLS
STEROID HORMONES
STEROIDS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques