scholarly journals Protein kinase C phosphorylation of rat liver S-adenosylmethionine synthetase: dissociation and production of an active monomer

1994 ◽  
Vol 303 (3) ◽  
pp. 949-955 ◽  
Author(s):  
M A Pajares ◽  
C Durán ◽  
F Corrales ◽  
J M Mato
Keyword(s):  
Alkaline Phosphatase ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Rat Liver ◽  
Oligomeric State ◽  
Kinase C ◽  
Phosphatase Treatment ◽  
Key Enzyme ◽  
Adenosylmethionine Synthetase ◽  
Adomet Synthetase

The regulation of rat liver S-adenosylmethionine synthetase (AdoMet synthetase), a key enzyme in methionine metabolism, by protein kinase C (PKC) phosphorylation has been studied. Both enzyme forms, tetramer and dimer, are phosphorylated by this kinase in the same residue, Thr-342, of the sequence. Phosphorylation of the dimer leads to its dissociation, with production of a fully-active monomer. The kinetics of the monomer have been studied, and a KmMet of 931.9 microM, a KmATP of 708 microM and a Vmax of 66.8 nmol/min/mg have been calculated. Alkaline phosphatase treatment of both enzyme forms (tetramer and dimer) produces a reduction in their activity with no change in the oligomeric state. On the other hand, PKC phosphorylation of the alkaline phosphatase-treated AdoMet synthetase forms leads to the dissociation of the dimer to produce a monomer. Rephosphorylation occurs again in the same residue, Thr-342, of the sequence. The significance of AdoMet synthetase regulation by PKC phosphorylation is further discussed.

Dephosphorylation of activated protein kinase C contributes to downregulation by bryostatin

1996 ◽  
Vol 271 (1) ◽  
pp. C304-C311 ◽  
Author(s):  
H. W. Lee ◽  
L. Smith ◽  
G. R. Pettit ◽  
J. Bingham Smith
Keyword(s):  
Alkaline Phosphatase ◽  
Protein Synthesis ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Bryostatin 1 ◽  
Rapid Loss ◽  
Renal Epithelial Cells ◽  
Kinase C ◽  
Phosphatase Treatment ◽  
Pkc Alpha

We show that bryostatin 1 (Bryo) rapidly produces an inactive, incompetent 76-kDa form of protein kinase C-alpha (PKC-alpha) in the LLC-MK2 line of renal epithelial cells. Bryo, like phorbol 12-myristate 13-acetate (PMA), acutely activated PKC, as indicated by autophosphorylation and translocation of PKC-alpha, the predominant PMA-sensitive isoform expressed by the cells. Bryo concomitantly increased the 32P labeling of 80-kDa PKC-alpha by autophosphorylation and produced a 76-kDa form of PKC-alpha that lacked detectable 32P. The 76-kDa form was in the particulate rather than the cytosolic fraction, which suggests that it was produced from activated kinase. Alkaline phosphatase treatment of immunoprecipitated PKC-alpha converted the 80-kDa form to 76 kDa, but it had no effect on the mobility of the 76-kDa form, suggesting that it was not phosphorylated. Pulse-chase labeling of PKC-alpha with [35S]Met/Cys indicated that there is a precursor-product relationship between the 80- and 76-kDa forms, respectively. Inhibition of protein synthesis had no effect on the production of 76-kDa PKC-alpha by Bryo. PMA also produced 76-kDa PKC-alpha but was less potent and efficacious than Bryo. Bryo produced a more rapid loss of 80-kDa PKC-alpha protein and total Ca(2+)- and phospholipid-dependent PKC activity than PMA. The 76-kDa form is inactive and incompetent because it lacked detectable 32P under conditions that strongly autophosphorylated the 80-kDa form. We suggest that dephosphorylation predisposes PKC to proteolysis, and greater production of the 76-kDa form explains the more efficient downregulation of the kinase by Bryo vs. PMA.

scholarly journals Phosphorylation of purified bovine heart and rat liver 6-phosphofructo-2-kinase by protein kinase C and comparison of the fructose-2,6-bisphosphatase activity of the two enzymes

1986 ◽  
Vol 240 (1) ◽  
pp. 57-61 ◽  
Author(s):  
M H Rider ◽  
L Hue
Keyword(s):  
Alkaline Phosphatase ◽  
Enzyme Activity ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Exchange Reaction ◽  
Liver Enzyme ◽  
Rat Liver ◽  
Phosphorylation State ◽  
Bovine Heart ◽  
Kinase C

Purified bovine heart 6-phosphofructo-2-kinase can be phosphorylated in the presence of protein kinase C and dephosphorylated by alkaline phosphatase; changes in phosphorylation state have no effect on enzyme activity. By contrast, the rat liver enzyme is a poor substrate for protein kinase C. Unlike the liver enzyme, which is bifunctional and is phosphorylated by fructose 2,6-[2-32P]bisphosphate, the heart enzyme contains 10 times less fructose 2,6-bisphosphatase activity and is phosphorylated at a slower rate and to a lesser extent than the liver enzyme. Both rat liver and bovine heart enzymes catalyse a similar exchange reaction between [U-14C]ADP and ATP.

scholarly journals Heterogeneous activation of protein kinase C during rat liver regeneration induced by carbon tetrachloride administration

FEBS Letters ◽  
1989 ◽  
Vol 254 (1-2) ◽  
pp. 59-65 ◽  
Author(s):  
Yutaka Sasaki ◽  
Norio Hayashi ◽  
Toshifumi Ito ◽  
Hideyuki Fusamoto ◽  
Nobuhiro Sato ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Carbon Tetrachloride ◽  
Protein Kinase ◽  
Liver Regeneration ◽  
Rat Liver ◽  
Rat Liver Regeneration ◽  
Kinase C ◽  
Carbon Tetrachloride Administration

Modulation of Rat Liver Protein Kinase C during in Vivo CC14-Induced Oxidative Stress

1993 ◽  
Vol 194 (2) ◽  
pp. 635-641 ◽  
Author(s):  
M.A. Pronzato ◽  
C. Domenicotti ◽  
E. Rosso ◽  
A. Bellocchio ◽  
M. Patrone ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Rat Liver ◽  
Liver Protein ◽  
Kinase C

Effects of protein kinase C and cytosolic Ca2+ on exocytosis in the isolated perfused rat liver

Hepatology ◽  
1994 ◽  
Vol 20 (4) ◽  
pp. 1032-1040 ◽  
Author(s):  
Rafael Bruck ◽  
Michael H. Nathanson ◽  
Han Roelofsen ◽  
James L. Boyer
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Rat Liver ◽  
Isolated Perfused Rat Liver ◽  
Perfused Rat Liver ◽  
Kinase C
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