Kinetic and Thermodynamic Analysis of Acetyl-CoA Activation of Staphylococcus aureus Pyruvate Carboxylase

Biochemistry. 2017 Jul 11;56(27):3492-3506. doi: 10.1021/acs.biochem.7b00383. Epub 2017 Jun 28.

Abstract

Allosteric regulation of pyruvate carboxylase (PC) activity is pivotal to maintaining metabolic homeostasis. In contrast, dysregulated PC activity contributes to the pathogenesis of numerous diseases, rendering PC a possible target for allosteric therapeutic development. Recent research efforts have focused on demarcating the role of acetyl-CoA, one of the most potent activators of PC, in coordinating catalytic events within the multifunctional enzyme. Herein, we report a kinetic and thermodynamic analysis of acetyl-CoA activation of the Staphylococcus aureus PC (SaPC)-catalyzed carboxylation of pyruvate to identify novel means by which acetyl-CoA synchronizes catalytic events within the PC tetramer. Kinetic and linked-function analysis, or thermodynamic linkage analysis, indicates that the substrates of the biotin carboxylase and carboxyl transferase domain are energetically coupled in the presence of acetyl-CoA. In contrast, both kinetic and energetic coupling between the two domains is lost in the absence of acetyl-CoA, suggesting a functional role for acetyl-CoA in facilitating the long-range transmission of substrate-induced conformational changes within the PC tetramer. Interestingly, thermodynamic activation parameters for the SaPC-catalyzed carboxylation of pyruvate are largely independent of acetyl-CoA. Our results also reveal the possibility that global conformational changes give rise to observed species-specific thermodynamic activation parameters. Taken together, our kinetic and thermodynamic results provide a possible allosteric mechanism by which acetyl-CoA coordinates catalysis within the PC tetramer.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetyl Coenzyme A / chemistry
  • Acetyl Coenzyme A / metabolism*
  • Adenosine Triphosphate / chemistry
  • Adenosine Triphosphate / metabolism
  • Algorithms
  • Allosteric Regulation
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Binding Sites
  • Biocatalysis
  • Energy Transfer
  • Enzyme Activation
  • Enzyme Stability
  • Kinetics
  • Magnesium / chemistry
  • Magnesium / metabolism
  • Models, Molecular*
  • Molecular Conformation
  • Protein Conformation
  • Protein Interaction Domains and Motifs
  • Protein Refolding
  • Pyruvate Carboxylase / chemistry
  • Pyruvate Carboxylase / genetics
  • Pyruvate Carboxylase / metabolism*
  • Pyruvic Acid / chemistry
  • Pyruvic Acid / metabolism
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Staphylococcus aureus / enzymology*
  • Thermodynamics

Substances

  • Bacterial Proteins
  • Recombinant Proteins
  • Acetyl Coenzyme A
  • Pyruvic Acid
  • Adenosine Triphosphate
  • Pyruvate Carboxylase
  • Magnesium