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Related Experiment Videos

THR246 mutations decrease substrate inhibition in lactate dehydrogenase.

R Sakowicz1, H Kallwass, W Parris

  • 1Department of Molecular and Medical Genetics, University of Toronto, Ontario, Canada.

Biochemical and Biophysical Research Communications
|February 14, 1992
PubMed
Summary
This summary is machine-generated.

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Site-directed mutagenesis of Bacillus stearothermophilus L-lactate dehydrogenase at threonine 246 reduced substrate inhibition. Eliminating a key hydrogen bond between threonine and pyruvate prevents the formation of an abortive complex, enhancing enzyme function.

Area of Science:

  • Biochemistry
  • Enzyme kinetics
  • Protein engineering

Background:

  • Bacillus stearothermophilus L-lactate dehydrogenase (L-LDH) is crucial in cellular metabolism.
  • Substrate inhibition by pyruvate can limit the efficiency of L-LDH.
  • Understanding the structural basis of substrate inhibition is key to enzyme engineering.

Purpose of the Study:

  • To investigate the role of Threonine 246 (T246) in pyruvate substrate inhibition of B. stearothermophilus L-LDH.
  • To engineer L-LDH variants with reduced or eliminated substrate inhibition.
  • To elucidate the structural mechanism underlying substrate inhibition.

Main Methods:

  • Site-directed mutagenesis was used to replace Threonine 246 with Valine (T246V), Serine (T246S), and Alanine (T246A).

Related Experiment Videos

  • Kinetic analyses were performed to assess the substrate inhibition patterns of the wild-type and mutant enzymes.
  • Structural analysis focused on the interaction between the enzyme, NAD+, and pyruvate.

    • Main Results:

    • The T246S mutant showed a decrease in pyruvate substrate inhibition.
    • The T246A and T246V mutants exhibited virtual elimination of substrate inhibition.
    • The absence of inhibition in T246A/V mutants is attributed to the disruption of a critical hydrogen bond between T246 and pyruvate.

    Conclusions:

    • Threonine 246 plays a critical role in mediating pyruvate substrate inhibition in B. stearothermophilus L-LDH.
    • Eliminating the hydrogen bond between T246 and pyruvate effectively abolishes substrate inhibition.
    • This study provides insights into enzyme inhibition mechanisms and offers strategies for enzyme engineering to improve catalytic efficiency.