Thermodynamic Linkages in Rabbit Muscle Pyruvate Kinase: Analysis of Experimental Data by a Two-State Model

James C. Lee, Robert W. Oberfelder, B. George Barisas

Research output: Contribution to journalArticle

28 Scopus citations

Abstract

A concerted, allosteric model is developed, and equations are derived for quantitative interpretation of the kinetic and equilibrium binding data of rabbit muscle pyruvate kinase at pH 7.5 and 23 °C. The simplest model which seems likely to rationalize the experimental data involves two conformational states. In this model, two simplifying assumptions are made. First, the affinities of pyruvate kinase for both substrate and inhibitor are assumed to depend only upon the conformational state of the tetrameric enzyme. Second, the rate of product formation is also assumed to depend only upon the enzyme conformation. All types of experimental data are analyzed simultaneously to estimate the parameters which best predict the total body of experimental results. The fitted parameters indicate that the intrinsic allosteric equilibrium favors the active (R) state by 11 to 1. The substrate phos-phoenolpyruvate binds preferentially, by a factor of 10, to the R state, whereas the inhibitor Phe has about 23 times higher affinity for the inactive (T) state. In all cases tested, the calculated values are in good agreement with the experimental data.

Original languageEnglish (US)
Pages (from-to)3822-3826
Number of pages5
JournalBiochemistry
Volume23
Issue number17
DOIs
StatePublished - Aug 1984

ASJC Scopus subject areas

  • Biochemistry

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