Protein Mass Effects on Formate Dehydrogenase.

Area of Science:

• Biochemistry
• Enzyme kinetics
• Protein dynamics

Background:

• Isotopically labeled enzymes (heavy enzymes) are used to probe the role of protein dynamics in catalysis.
• The hypothesis is that increased protein mass alters vibrational frequencies without changing electrostatics.
• Previous studies on heavy enzymes have yielded ambiguous results regarding their impact on catalysis.

Purpose of the Study:

• To investigate the temperature-dependence of kinetic isotope effects in formate dehydrogenase using heavy enzymes.
• To examine how protein mass influences the distribution of H-donor to H-acceptor distances during catalysis.
• To differentiate between Born-Oppenheimer (vibrational) and non-Born-Oppenheimer (electrostatic) effects in enzyme catalysis.

Main Methods:

• Utilized temperature-dependence of intrinsic kinetic isotope effects.
• Employed steady-state and single-turnover measurements.
• Analyzed protein mass dependence of donor-acceptor distance and forward commitment to catalysis.

Main Results:

• Heavy enzyme dynamics were altered, diminishing motions critical for transition state sampling.
• Findings suggest contributions from both fast, vibrational (Born-Oppenheimer) and slower, electrostatic (non-Born-Oppenheimer) processes.
• Protein mass modulation impacted local vibrations and macromolecular electrostatics.

Conclusions:

• Both Born-Oppenheimer and non-Born-Oppenheimer effects are observed in heavy enzyme studies.
• Isotopic labeling can have system-specific effects on enzyme dynamics.
• Heavy enzyme studies are a valuable technique for investigating the link between protein dynamics and catalysis.