Hepatic pyruvate kinase. Regulation by glucagon, cyclic adenosine 3'-5'-monophosphate, and insulin in the perfused rat liver - PubMed (original) (raw)
. 1976 Jun 25;251(12):3756-62.
- PMID: 180008
Free article
Hepatic pyruvate kinase. Regulation by glucagon, cyclic adenosine 3'-5'-monophosphate, and insulin in the perfused rat liver
J B Blair et al. J Biol Chem. 1976.
Free article
Abstract
A reversible interconversion of two kinetically distinct forms of hepatic pyruvate kinase regulated by glucagon and insulin is demonstrated in the perfused rat liver. The regulation does not involve the total enzyme content of the liver, but rather results in a modulation of the substrate dependence. The forms of pyruvate kinase in liver homogenates are distinguished by measurements of the ratio of the enzyme activity at a subsaturating concentration of P-enolpyruvate (1.3 mM) to the activity at a saturating concentration of this substrate (6.6 mM). A low ratio form of pyruvate kinase (ratio between 0.1 and 0.2) is obtained from livers perfused with 10(-7) M glucagon or 0.1 mM adenosine 3':5'-monophosphate (cyclic AMP). A high ratio form of the enzyme is obtained from livers perfused with no hormone (ratio = 0.35 to 0.45). The regulation of pyruvate kinase by glucagon and cyclic AMP occurs within 2 min following the hormone addition to the liver. Insulin (22 milliunits/ml) counteracts the inhibition of pyruvate kinase caused by 5 X 10(-11) M glucagon, but has only a slight influence on the enzyme properties in the absence of the hyperglycemic hormone. The low ratio form of pyruvate kinase obtained from livers perfused with glucagon or cyclic AMP is unstable in liver extracts and will revert to a high ratio form within 10 min at 37 degrees or within a few hours at 0 degrees. Pyruvate kinase is quantitatively precipitated from liver supernatants with 2.5 M ammonium sulfate. This precipitation stabilizes the enzyme and preserves the kinetically distinguishable forms. The kinetic properties of the two forms of rat hepatic pyruvate kinase are examined using ammonium sulfate precipitates from the perfused rat liver. At pH 7.5 the high ratio form of the enzyme has [S]0.5 = 1.6 +/- 0.2 mM P-enolpyruvate (n = 8). The low ratio form of enzyme from livers perfused with glucagon or cyclic AMP has [S]0.5 = 2.5 +/- 0.4 mM P-enolpyruvate (n = 8). The modification of pyruvate kinase induced by glucagon does not alter the dependence of the enzyme activity on ADP (Km is approximately 0.5 mM ADP for both forms of the enzyme). Both forms are allosterically modulated by fructose 1,6-bisphosphate, L-alanine, and ATP. The changes in the kinetic properties of hepatic pyruvate kinase which follow treating the perfused rat liver with glucagon or cyclic AMP are consistent with the changes observed in the enzyme properties upon phosphorylation in vitro by a clyclic AMP-stimulated protein kinase (Ljungström, O., Hjelmquist, G. and Engström, L. (1974) Biochim. Biophys. Acta 358, 289--298). However, other factors also influence the enzyme activity in a similar manner and it remains to be demonstrated that the regulation of hepatic pyruvate kinase by glucagon and cyclic AMP in vivo involes a phosphorylation.
Similar articles
- Modulation of the phosphorylation state of rat liver pyruvate kinase by allosteric effectors and insulin.
Claus TH, El-Maghrabi MR, Pilkis SJ. Claus TH, et al. J Biol Chem. 1979 Aug 25;254(16):7855-64. J Biol Chem. 1979. PMID: 468793 - Hormonal control of pyruvate kinase activity and of gluconeogenesis in isolated hepatocytes.
Feliú JE, Hue L, Hers HG. Feliú JE, et al. Proc Natl Acad Sci U S A. 1976 Aug;73(8):2762-6. doi: 10.1073/pnas.73.8.2762. Proc Natl Acad Sci U S A. 1976. PMID: 183209 Free PMC article. - Comparative kinetic studies on the L-type pyruvate kinase from rat liver and the enzyme phosphorylated by cyclic 3', 5'-AMP-stimulated protein kinase.
Ekman P, Dahlqvist U, Humble E, Engström L. Ekman P, et al. Biochim Biophys Acta. 1976 Apr 8;429(2):374-82. doi: 10.1016/0005-2744(76)90285-0. Biochim Biophys Acta. 1976. PMID: 4127 - Dephosphorylation of L-pyruvate kinase during rat liver hepatocyte isolation.
Riou JP, Audigier C, Laville M, Beylot M, Pigeon P, Mornex R. Riou JP, et al. Arch Biochem Biophys. 1985 Jan;236(1):321-7. doi: 10.1016/0003-9861(85)90632-0. Arch Biochem Biophys. 1985. PMID: 2981507
Cited by
- Glucagon, cyclic AMP, and hepatic glucose mobilization: A half-century of uncertainty.
Rodgers RL. Rodgers RL. Physiol Rep. 2022 May;10(9):e15263. doi: 10.14814/phy2.15263. Physiol Rep. 2022. PMID: 35569125 Free PMC article. Review. - Mass spectrometry-based microassay of (2)H and (13)C plasma glucose labeling to quantify liver metabolic fluxes in vivo.
Hasenour CM, Wall ML, Ridley DE, Hughey CC, James FD, Wasserman DH, Young JD. Hasenour CM, et al. Am J Physiol Endocrinol Metab. 2015 Jul 15;309(2):E191-203. doi: 10.1152/ajpendo.00003.2015. Epub 2015 May 19. Am J Physiol Endocrinol Metab. 2015. PMID: 25991647 Free PMC article. - Physiological and metabolic changes associated with weaning in the tammar wallaby, Macropus eugenii.
Wilkes GE, Janssens PA. Wilkes GE, et al. J Comp Physiol B. 1986;156(6):829-37. doi: 10.1007/BF00694258. J Comp Physiol B. 1986. PMID: 3794017 - Development of gluconeogenesis from dihydroxyacetone in rat hepatocytes during a feeding cycle and starvation.
Azzout B, Peret J. Azzout B, et al. Biochem J. 1984 Mar 15;218(3):975-81. doi: 10.1042/bj2180975. Biochem J. 1984. PMID: 6721842 Free PMC article.