scholarly journals Use of rapid gel-permeation chromatography to explore the inter-relationships between polymerization, phosphorylation and activity of acetyl-CoA carboxylase. Effects of insulin and phosphorylation by cyclic AMP-dependent protein kinase

1987 ◽  
Vol 241 (3) ◽  
pp. 773-782 ◽  
Author(s):  
A C Borthwick ◽  
N J Edgell ◽  
R M Denton
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Degree Of Polymerization ◽  
Beta Agonist ◽  
Epididymal Adipose Tissue ◽  
Acetyl Coa Carboxylase ◽  
Dependent Protein Kinase ◽  
Acetyl Coa ◽  
Polymeric Form ◽  
Dependent Protein

Superose 6 chromatography was used to separate rapidly the polymeric and dimeric forms of acetyl-CoA carboxylase. With preparations of acetyl-CoA carboxylase purified by Sepharose-avidin chromatography, it is shown that citrate promotes polymerization and that the extent of polymerization is diminished, but not eliminated, after phosphorylation by cyclic-AMP-dependent protein kinase. After exposure of rat epididymal adipose tissue to insulin, evidence was obtained for a marked increase in polymerization. The polymeric form, which was active in the absence of citrate, exhibited increased phosphorylation, particularly on a tryptic peptide designated the I-peptide in an earlier study [Brownsey & Denton (1982) Biochem. J. 202, 77-86]. In contrast, in tissue exposed to the beta-agonist isoprenaline, most of the phosphorylated acetyl-CoA carboxylase appeared to be in the dimeric form if chromatography was carried out in the absence of citrate, whereas in the presence of citrate the degree of polymerization was diminished.

scholarly journals Evidence that glucagon-mediated inhibition of acetyl-CoA carboxylase in isolated adipocytes involves increased phosphorylation of the enzyme by cyclic AMP-dependent protein kinase

1985 ◽  
Vol 226 (1) ◽  
pp. 139-145 ◽  
Author(s):  
R Holland ◽  
D G Hardie ◽  
R A Clegg ◽  
V A Zammit
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Kinetic Parameters ◽  
Acetyl Coa Carboxylase ◽  
Response Curves ◽  
Dependent Protein Kinase ◽  
Acetyl Coa ◽  
Dependent Protein ◽  
Isolated Adipocytes

The kinetic parameters and phosphorylation state of acetyl-CoA carboxylase were analysed after purification of the enzyme by avidin-Sepharose chromatography from extracts of isolated adipocytes treated with glucagon or adrenaline. The results provide evidence that the mechanism of inhibition of acetyl-CoA carboxylase in adipocytes treated with glucagon [Zammit & Corstorphine (1982) Biochem. J. 208, 783-788] involves increased phosphorylation of the enzyme. Hormone treatment had effects on the kinetic parameters of the enzyme similar to those of phosphorylation of the enzyme in vitro by cyclic AMP-dependent protein kinase. Glucagon treatment of adipocytes led to increased phosphorylation of acetyl-CoA carboxylase in the same chymotryptic peptide as that containing the major site phosphorylated on the enzyme by purified cyclic AMP-dependent protein kinase in vitro [Munday & Hardie (1984) Eur. J. Biochem. 141, 617-627]. The dose-response curves for inhibition of enzyme activity and increased phosphorylation of the enzyme were very similar, with half-maximal effects occurring at concentrations of glucagon (0.5-1 nM) which are close to the physiological range. In general, the patterns of increased 32P-labelling of chymotryptic peptides induced by glucagon or adrenaline were similar, although there were quantitative differences between the effects of the two hormones on individual peptides. The results are discussed in terms of the possible roles of cyclic AMP-dependent and -independent protein kinases in the regulation of acetyl-CoA carboxylase activity and of lipogenesis in white adipose tissue.

scholarly journals Studies on insulin-stimulated phosphorylation of acetyl-CoA carboxylase, ATP citrate lyase and other proteins in rat epididymal adipose tissue. Evidence for activation of a cyclic AMP-independent protein kinase

1984 ◽  
Vol 218 (3) ◽  
pp. 733-743 ◽  
Author(s):  
R W Brownsey ◽  
N J Edgell ◽  
T J Hopkirk ◽  
R M Denton
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
High Speed ◽  
Kinase Activity ◽  
Epididymal Adipose Tissue ◽  
Protein Kinase Activity ◽  
Acetyl Coa Carboxylase ◽  
Atp Citrate Lyase ◽  
Acetyl Coa ◽  
Citrate Lyase

Protein kinase activity in high-speed supernatant fractions prepared from rat epididymal adipose tissue previously incubated in the absence or presence of insulin was investigated by following the incorporation of 32P from [gamma-32P]ATP into phosphoproteins separated by sodium dodecyl sulphate/polyacrylamide-gel electro-phoresis. Incorporation of 32P into several endogenous proteins in the supernatant fractions from insulin-treated tissue was significantly increased. These included acetyl-CoA carboxylase and ATP citrate lyase (which exhibit increased phosphorylation within fat-cells exposed to insulin), together with two unknown proteins of subunit Mr 78000 and 43000. The protein kinase activity increased by insulin was distinct from cyclic AMP-dependent protein kinase, was not dependent on Ca2+ and was not appreciably affected by dialysis or gel filtration. The rate of phosphorylation of added purified fat-cell acetyl-CoA carboxylase and ATP citrate lyase was also increased by 60-90% in high-speed-supernatant fractions prepared from insulin-treated tissue. No evidence for any persistent changes in phosphoprotein phosphatase activity was found. It is concluded that insulin action on acetyl-CoA carboxylase, ATP citrate lyase and other intracellular proteins exhibiting increased phosphorylation involves an increase in cyclic AMP-independent protein kinase activity in the cytoplasm. The possibility that the increase reflects translocation from the plasma membrane, perhaps after phosphorylation by the protein tyrosine kinase associated with insulin receptors, is discussed.

scholarly journals The short-term regulation of hepatic acetyl-CoA carboxylase during starvation and re-feeding in the rat

1991 ◽  
Vol 280 (3) ◽  
pp. 733-737 ◽  
Author(s):  
M R Munday ◽  
M R Milic ◽  
S Takhar ◽  
M J Holness ◽  
M C Sugden
Keyword(s):  
Protein Kinase ◽  
Rat Liver ◽  
Acetyl Coa Carboxylase ◽  
Short Term ◽  
Dependent Protein Kinase ◽  
Acetyl Coa ◽  
Plasma Insulin Concentration ◽  
Dependent Protein ◽  
Time Courses ◽  
Amp Activated Protein Kinase

Rapid inhibition of acetyl-CoA carboxylase (ACC) activity in rat liver in response to 6 h starvation and rapid re-activation in response to 2-6 h of re-feeding chow were shown to be due to changes in the expressed activity of existing enzyme. Decreases and increases in ACC concentration occurred at later stages of the transitions, i.e. 6-48 h starvation and 8-24 h re-feeding respectively. The decrease in expressed activity of ACC was due primarily to changes in its phosphorylation state, demonstrated by a significantly decreased Vmax. and significantly increased Ka for citrate of enzyme purified by avidin-Sepharose chromatography from 6 h- or 48 h-starved rats. These effects were totally reversed within 2-4 h of chow re-feeding. Changes in the activity of purified ACC closely correlated with reciprocal changes in the activity of AMP-activated protein kinase (AMP-PK) over the fed to starved to re-fed transition. Increases in the activity ratio of cyclic-AMP-dependent protein kinase in response to starvation lagged behind the increase in AMP-PK and the decrease in ACC activity. Changes in AMP-PK and ACC activities of rat liver closely correlated with changes in plasma insulin concentration in response to time courses of starvation and re-feeding.

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