Regulation <i>in vitro</i> and <i>in vivo</i> of Adenosine 3′:5′‐monophosphate‐Dependent Inactivation of Rat‐Liver Pyruvate Kinase Type L

Feliu, Jaume Cruz i; Hue, Louis; Hers, Henri‐Géry

doi:10.1111/j.1432-1033.1977.tb11988.x

Cited by 85 publications

(45 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…(In agreement with Feliu et al [20] it was found that the inactivation reaction rate with isolated hepatocyte supernatant is half-maximal at about 0.1 pM cAMP and maximal above 1 pM CAMP. For human liver these values are respectively 0.04 pM and 0.5 pM [21].)…”

Section: Effect Of Starvationsupporting

confidence: 76%

“…This can solve the problem of the specificity of liver protein kinases for their various substrates because regulation of protein kinase activity on a special substrate may now be exerted by the structure (influenced by effectors) of the substrates. This way of regulation was proposed on the basis of experiments in vitro [20] and on data obtained in a purified system [29,30]. Our results can be used as an indication that it can operate inside the cell.…”

Section: Effect Of Glucagon Upon Hepatocytes Of Starved Animalsmentioning

confidence: 67%

See 1 more Smart Citation

Difference in the Effect of Glucagon and Starvation upon l‐Type Pyruvate Kinase from Rat Liver

Berkel

Kruijt

Berg

et al. 1978

European Journal of Biochemistry

View full text Add to dashboard Cite

1. The mechanism of the glucagon action upon pyruvate kinase in isolated hepatocytes from fed or starved rats has been investigated. Glucagon incubation of hepatocytes increases the reaction responsible for pyruvate kinase inactivation. This inactivation reaction is completely dependent upon the presence of adenosine 3': 5'-monophosphate (CAMP), (half maximal activation at 0.1 pM CAMP) with cells incubated without glucagon, while with cells incubated with glucagon CAMP addition only has a marginal effect. It is concluded that glucagon acts by activation of the protein kinase responsible for pyruvate kinase inactivation.2. Glucagon addition to isolated hepatocytes from fed and starved rats causes a similar decrease in pyruvate kinase activity of 40.7 2.5% and 36.6 f 3.6%, respectively, when measured at suboptimal phosphoenolpyruvate concentrations. Although optimal concentrations of glucagon (1 pM) are used during the cell incubations, the pyruvate kinase activity can be inactivated further in vitro by incubation under conditions for optimal protein kinase activity. From the kinetic curves for the substrate phosphoenolpyruvate, obtained before and after further incubation in vitro, it can be concluded that pyruvate kinase by its presence inside the cell is protected against a complete inactivation by glucagon.3. The difference in apparent affinity of pyruvate kinase for phosphoenolpyruvate from glucagonincubated cells versus cells incubated without glucagon disappears after further incubation of the supernatants of these cells in vitro under optimal conditions for protein kinase activity (plus 10 pM CAMP) and an enzyme with a low affinity for phosphoenolpyruvate is obtained (Ko.5 = 4.4 mM). These results indicate that the glucagon-induced change in kinetic properties of pyruvate kinase can be adequately explained by an increased phosphorylation state of pyruvate kinase.4. The difference in apparent affinity of pyruvate kinase for phosphoenolpyruvate from fed liver versus starved liver (P < 0.001) still persists after further incubation of the liver supernatants under optimal conditions for protein kinase activity in vitro ( P < 0.001). For the completely inactivated enzyme from livers of fed and starved rats K0.5 values for phosphoenolpyruvate of respectively 2.8 and 4.4 mM are obtained. These results indicate that the nature of the effect of starvation differs from that of glucagon. It is suggested that the effect of starvation might be caused by partial proteolysis of the enzyme or oxidation of essential thiol groups.L-type pyruvate kinase has been shown to be a site of glucagon action in the hepatic gluconeogenic pathway [l-61. The mechanism of glucagon action has been investigated with isolated hepatocytes [7] and liver slices [8]. The glucagon-inhibited enzyme in hepatocytes can be reactivated in vitro, which reactivation is promoted by Mg2' and blocked by F- [7]. These properties are most consistent with a protein phosphatase mediated process implying that the glucagon-induced inactivation is the consequen...

show abstract

Section: Effect Of Starvationsupporting

confidence: 76%

Section: Effect Of Glucagon Upon Hepatocytes Of Starved Animalsmentioning

confidence: 67%

Difference in the Effect of Glucagon and Starvation upon l‐Type Pyruvate Kinase from Rat Liver

Berkel

Kruijt

Berg

et al. 1978

European Journal of Biochemistry

View full text Add to dashboard Cite

show abstract

“…Frozen plates were scraped with 100 l of a homogenization buffer at pH 7.4 with 50 mM glycylglycine, 15 mM EDTA, 100 mM KF, and 5 mM potassium phosphate. The homogenates were centrifuged at 10,000 ϫ g for 15 min at 4°C, and total PK activity and activity ratio (V 0.15 /V, measured at 0.15 and 5 mM phosphoenolpyruvate, respectively) were determined in the supernatants as described (17).…”

Section: Methodsmentioning

confidence: 99%

Glucokinase Overexpression Restores Glucose Utilization and Storage in Cultured Hepatocytes from Male Zucker Diabetic Fatty Rats

Seoane¹,

Barberà²,

Télémaque-Potts³

et al. 1999

Journal of Biological Chemistry

View full text Add to dashboard Cite

Zucker diabetic fatty rats develop type 2 diabetes concomitantly with peripheral insulin resistance. Hepatocytes from these rats and their control lean counterparts have been cultured, and a number of key parameters of glucose metabolism have been determined. Glucokinase activity was 4.5-fold lower in hepatocytes from diabetic rats than in hepatocytes from healthy ones. In contrast, hexokinase activity was about 2-fold higher in hepatocytes from diabetic animals than in healthy ones. Glucose-6-phosphatase activity was not significantly different. Despite the altered ratios of glucokinase to hexokinase activity, intracellular glucose 6-phosphate concentrations were similar in the two types of cells when they where incubated with 1-25 mM glucose. However, glycogen levels and glycogen synthase activity ratio were lower in hepatocytes from diabetic animals. Total pyruvate kinase activity and its activity ratio as well as fructose 2,6-bisphosphate concentration and lactate production were also lower in cells from diabetic animals. All of these data indicate that glucose metabolism is clearly impaired in hepatocytes from Zucker diabetic fatty rats.Glucokinase overexpression using adenovirus restored glucose metabolism in diabetic hepatocytes. In glucokinase-overexpressing cells, glucose 6-phosphate levels increased. Moreover, glycogen deposition was greatly enhanced due to the activation of glycogen synthase. Pyruvate kinase was also activated, and fructose-2,6-bisphosphate concentration and lactate production were increased in glucokinase-overexpressing diabetic hepatocytes. Overexpression of hexokinase I did not increase glycogen deposition. In conclusion, hepatocytes from Zucker diabetic fatty rats showed depressed glycogen and glycolytic metabolism, but glucokinase overexpression improved their glucose utilization and storage.

show abstract

“…These activities were analyzed in 12,000 g as described in references 56 and 57, respectively. Pyruvate kinase activity was determined at 0.15 mM P-enolpyruvate (active form) and at 5 mM P-enolpyruvate (total activity) (56). Glucokinase activity was calculated as the difference between the glucose phosphorylation capacity at 100 and 0.5 mM glucose (57).…”

Section: Introductionmentioning

confidence: 99%

Vanadate treatment restores the expression of genes for key enzymes in the glucose and ketone bodies metabolism in the liver of diabetic rats.

Valera¹,

Rodríguez‐Gil²,

Bosch³

1993

J. Clin. Invest.

View full text Add to dashboard Cite

Oral administration of vanadate to diabetic streptozotocintreated rats decreased the high blood glucose and D-3-hydroxybutyrate levels related to diabetes. The increase in the expression of the P-enolpyruvate carboxykinase (PEPCK) gene, the main regulatory enzyme of gluconeogenesis, was counteracted in the liver and the kidney after vanadate administration to diabetic rats. Vanadate also counteracted the induction in tyrosine aminotransferase gene expression due to diabetes and was able to increase the expression of the glucokinase gene to levels even higher than those found in healthy animals. Similarly, an induction in pyruvate kinase mRNA transcripts was observed in diabetic vanadate-treated rats. These effects were correlated with changes on glucokinase and pyruvate kinase activities. Vanadate treatment caused a decrease in the expression of the liver-specific glucose transporter, GLUT-2. Thus, vanadate was able to restore liver glucose utilization and block glucose production in diabetic rats. The increase in the expression of the mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (HMGCoAS) gene, the key regulatory enzyme in the ketone bodies production pathway, observed in diabetic rats was also blocked by vanadate. Furthermore, a similar pattern in the expression of PEPCK, GLUT-2, HMGCoAS, and the transcription factor CCAAT/ enhancer-binding protein a genes has been observed. All of these results suggest that the regulation of the expression of genes involved in the glucose and ketone bodies metabolism could be a key step in the normalization process induced by vanadate administration to diabetic rats. (J. Clin.

show abstract

Regulation in vitro and in vivo of Adenosine 3′:5′‐monophosphate‐Dependent Inactivation of Rat‐Liver Pyruvate Kinase Type L

Cited by 85 publications

References 34 publications

Difference in the Effect of Glucagon and Starvation upon l‐Type Pyruvate Kinase from Rat Liver

Difference in the Effect of Glucagon and Starvation upon l‐Type Pyruvate Kinase from Rat Liver

Glucokinase Overexpression Restores Glucose Utilization and Storage in Cultured Hepatocytes from Male Zucker Diabetic Fatty Rats

Vanadate treatment restores the expression of genes for key enzymes in the glucose and ketone bodies metabolism in the liver of diabetic rats.

Contact Info

Product

Resources

About