HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 277, Issue 30, 27176-27182, July 26, 2002

This Article Full Text Full Text (PDF) All Versions of this Article: 277/30/27176    most recent M111422200v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Dobson, G. P. Articles by Teague, W. E. Search for Related Content PubMed PubMed Citation Articles by Dobson, G. P. Articles by Teague, W. E., Jr. Social Bookmarking                      What's this?

Thermodynamics of the Pyruvate Kinase Reaction and the Reversal of Glycolysis in Heart and Skeletal Muscle^*

Geoffrey P. Dobson^§, Sam Hitchins, and Walter E. Teague Jr.^¶

From the  Division of Physiology and Pharmacology, School of Biomedical and Molecular Sciences, James Cook University, Townsville, Queensland 4811, Australia and the ^¶ Section of Nuclear Magnetic Resonance Studies, Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, Rockville, Maryland 20852

The effect of temperature, pH, and free [Mg²⁺] on the apparent equilibrium constant of pyruvate kinase (phosphoenol transphosphorylase) (EC 2.7.1.40) was investigated. The apparent equilibrium constant, K', for the biochemical reaction P-enolpyruvate + ADP = ATP + Pyr was defined as K' = [ATP][Pyr]/[ADP][P-enolpyruvate], where each reactant represents the sum of all the ionic and metal complexed species in M. The K' at pH 7.0, 1.0 mM free Mg²⁺ and I of 0.25 M was 3.89 × 10⁴ (n = 8) at 25 °C. The standard apparent enthalpy (H'°) for the biochemical reaction was 4.31 kJmol¹ in the direction of ATP formation. The corresponding standard apparent entropy (S'°) was +73.4 J K¹ mol¹. The H° and S° values for the reference reaction, P-enolpyruvate³ + ADP³ + H⁺ = ATP⁴ + Pyr¹, were 6.43 kJmol¹ and +180 J K¹ mol¹, respectively (5 to 38 °C). We examined further the mass action ratio in rat heart and skeletal muscle at rest and found that the pyruvate kinase reaction in vivo was close to equilibrium i.e. within a factor of about 3 to 6 of K' in the direction of ATP at the same pH, free [Mg²⁺], and T. We conclude that the pyruvate kinase reaction may be reversed under some conditions in vivo, a finding that challenges the long held dogma that the reaction is displaced far from equilibrium.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

This article has been cited by other articles:

				B. Weiss The Deoxycytidine Pathway for Thymidylate Synthesis in Escherichia coli J. Bacteriol., November 1, 2007; 189(21): 7922 - 7926. [Abstract] [Full Text] [PDF]