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Breaking the covalent connection: Chain connectivity and the catalytic reaction of PMM/PGM

Andrew M Schramm1, Dale Karr, Ritcha Mehra-Chaudhary

  • 1Department of Biochemistry, University of Missouri, Columbia, Missouri 65211, USA.

Protein Science : a Publication of the Protein Society
|June 1, 2010
PubMed

Insights

Investigating phosphomannomutase/phosphoglucomutase (PMM/PGM) chain connectivity revealed that a flexible C-terminal domain negatively impacts catalytic efficiency due to increased entropy, highlighting the importance of polypeptide chain integrity.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Enzymology

Background:

  • Phosphomannomutase/phosphoglucomutase (PMM/PGM) is crucial for carbohydrate metabolism in Pseudomonas aeruginosa.
  • Understanding enzyme structure-function relationships, particularly chain connectivity, is vital for drug development.

Purpose of the Study:

  • To investigate the role of polypeptide chain connectivity in the catalytic activity of PMM/PGM.
  • To determine how domain flexibility affects enzyme efficiency.

Main Methods:

  • Fragment complementation was used to create a heterodimer of PMM/PGM from separate domain fragments.
  • Nuclear Magnetic Resonance (NMR) spectroscopy was employed to analyze domain structure.
  • Steady-state kinetics and thermodynamic studies were performed to assess enzyme activity.

Main Results:

  • The C-terminal domain (Domain 4) of PMM/PGM functions as a highly structured, independent folding unit.
  • Breaking the polypeptide chain to create a flexible Domain 4 significantly reduced catalytic efficiency.
  • Increased entropic cost associated with Domain 4's conformational freedom was identified as the primary reason for reduced efficiency.

Conclusions:

  • Polypeptide chain integrity is essential for optimal catalytic efficiency in PMM/PGM.
  • Enzyme flexibility, controlled by amino acid sequence and evolutionary constraints, impacts catalytic performance.
  • Combining separate folding domains into a single polypeptide chain offers functional advantages for enzyme activity.

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