Concentrations of Metabolites and Binding Sites. Implications in Metabolic Regulation

Sols, Alberto; Marco, Roberto de

doi:10.1016/b978-0-12-152802-7.50013-x

Cited by 221 publications

(73 citation statements)

References 90 publications

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“…However, the clear evidence that the enzymatic inactivation of pyruvate kinase does occur in isolated liver preparations [3 -61 and in vivo (present paper) indicates that the concentration of free fructose bisphosphate in the liver cell is extremely low. The conclusion that most of the fructose bisphosphate present in the liver is bound to protein has previously been reached by other authors [31]. There may also be other factors, yet unknown, which modulate the effect of fructose bisphosphate on the inactivation of pyruvate kinase.…”

Section: Stimulators and Inhibitors Of The Phosphorylation Of Pyruvatmentioning

confidence: 77%

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

Feliu

Hue²,

Hers³

1977

European Journal of Biochemistry

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The cyclic-AMP-dependent inactivation of pyruvate kinase L has been studied in a crude Sephadex filtrate of isolated hepatocytes. This inactivation requires the presence of Mg-ATP (apparent K, = 0.1 inM) and a half-maximal rate of inactivation was obtained in the presence of 0.1 5 JAM cyclic AMP. It was inhibited by physiological concentrations of phosphoenolpyruvate and by micromolar concentrations of fructose bisphosphate and these inhibitory effects were counteracted by Mg-ATP and by several L-form amino acids such as cysteine, alanine, serine, phenylalanine, which are also ligands of pyruvate kinase. As a rule, it appears that effectors that increase the activity of the enzyme are also those which prevent its cyclic-AMP-dependent inactivation and vice-versa.Considering the potentially important role of phosphoenolpyruvate concentration in the control of gluconeogenesis, experiments were performed to check if the inhibitory action of this metabolite on the inactivation of pyruvate kinase was of importance in vivo. We found that the concentration of phosphoenolpyruvate was higher than normal in the livers of anesthetized rats in conditions like fasting and diabetes in which the rate of gluconeogenesis is known to be higher and the activity of pyruvate kinase lower than normally. The reverse was true upon sucrose feeding. Inactivation of pyruvate kinase was induced in vivo by the administration of glucagon. This inactivation was less important in the livers with high concentrations of phosphoenolpyruvate and vice-versa. It is proposed that phosphoenolpyruvate exerts an important buffering effect in the variations of the rate of gluconeogenesis.Purified liver pyruvate kinase L can be inactivated through phosphorylation by cyclic-AMP-dependent protein kinase [l ] and reactivated by dephosphorylation catalyzed by histone phosphatase [2]. Treatment of isolated liver preparations with cyclic AMP or glucagon causes modifications of the kinetic properties of pyruvate kinase [3 -61 that are similar to those found in vitro after phosphorylation of purified liver pyruvate kinase [7,8]. The fact that the inactivation of pyruvate kinase by glucagon, cyclic AMP and epinephrine in isolated hepatocytes is parallel with a stimulation of gluconeogenesis, strongly suggests that phosphorylation of pyruvate kinase plays a

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Section: Stimulators and Inhibitors Of The Phosphorylation Of Pyruvatmentioning

confidence: 77%

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

Feliu

Hue²,

Hers³

1977

European Journal of Biochemistry

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“…This paper examines scheme (la) when there is an excess of enzyme, so that (lb) does not hold. The classical QSSA breaks down in these situations, which can be encountered in viuo (Straus and Goldstein, 1943, p. 581;Sols and Marco, 1970) or in biotechnological applications. Remarkably, a simple change of variable permits the validity of the classical QSSA to be considerably extended so that the new situations are covered in many instances.…”

Section: Introduction Prototypical In Biochemistry Is the Reversiblementioning

confidence: 99%

Extending the quasi-steady state approximation by changing variables

Borghans

1996

Bulletin of Mathematical Biology

178

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“…cerevisiae synthesizes two or more isomers of several of the enzymes that catalyse reactions on the Embden-Meyerhof-Parnas pathway (Fraenkel,198 1). Moreover, several reports indicate that the enzymes may be membranebound (Rothstein et al, 1959;Green et al, 1965;Atkinson, 1969;Sols & Marco, 1970), although it has yet to be demonstrated that they exist in a multi-enzyme complex as in Escherichia coli (Mowbray & Moses, 1976).…”

Section: Introductionmentioning

confidence: 99%

Production and Tolerance of Ethanol in Relation to Phospholipid Fatty-acyl Composition in Saccharomyces cerevisiae NCYC 431

1982

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Accumulation of ethanol in supernatants from anaerobic cultures of Saccharomyces cerevisiae NCYC 43 1 closely paralleled growth during the early exponential phase of batch growth, and continued after growth had ceased. During the 8-64 h period of the fermentation, the intracellular ethanol concentration was greater than the extracellular concentration. Ethanol was very rapidly extracted from organisms by washing with water. During growth up to 32 h, there was a progressive decrease in fatty-acyl unsaturation in phospholipids, and a corresponding proportional increase in saturation. Thereafter, the trend was very slightly reversed. Supplementing cultures with ethanol (0.5 or 1.0 M) after 8 h incubation retarded growth rate, while supplementation with 1.5 M-ethanol immediately stopped growth. In cultures supplemented with 0.5 or 1 SO M-ethanol, viability was not lowered, but supplementation with 1 -5 M-ethanol caused a rapid decline in viability.Supplementation of cultures with ethanol at any of the three concentrations led to an increase in the proportion of mono-unsaturated fatty-acyl residues in cellular phospholipids, especially in CI8 residues, which was accompanied by a decrease in the proportion of saturated residues.

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Concentrations of Metabolites and Binding Sites. Implications in Metabolic Regulation

Cited by 221 publications

References 90 publications

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

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

Extending the quasi-steady state approximation by changing variables

Production and Tolerance of Ethanol in Relation to Phospholipid Fatty-acyl Composition in Saccharomyces cerevisiae NCYC 431

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