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Related Experiment Videos

Single-molecule enzymatic dynamics

H P Lu1, L Xun, X S Xie

  • 1Pacific Northwest National Laboratory, William R. Wiley Environmental Molecular Sciences Laboratory, Richland, WA 99352, USA.

Science (New York, N.Y.)
|December 4, 1998
PubMed
Summary
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Single-molecule observations revealed slow fluctuations in cholesterol oxidase activity, distinguishing static and dynamic rate disorders. This study uncovered a molecular memory effect due to protein conformational changes affecting enzyme turnover.

Area of Science:

  • Biochemistry
  • Enzymology
  • Single-molecule biophysics

Background:

  • Cholesterol oxidase catalyzes cholesterol oxidation using flavin adenine dinucleotide (FAD) as a cofactor.
  • Ensemble-averaged experiments often mask the heterogeneity and dynamic behavior of individual enzyme molecules.
  • Understanding enzyme dynamics is crucial for elucidating reaction mechanisms.

Purpose of the Study:

  • To investigate the real-time enzymatic turnover of single cholesterol oxidase molecules.
  • To differentiate between static and dynamic disorder in enzyme reaction rates.
  • To explore potential molecular memory phenomena in enzymatic reactions.

Main Methods:

  • Real-time observation of single cholesterol oxidase molecules using fluorescence monitoring of the active site FAD.

Related Experiment Videos

  • Statistical analysis of single-molecule trajectories to determine reaction rate fluctuations.
  • Separation of static and dynamic disorder components of reaction rates.

    • Main Results:

    • Significant and slow fluctuations in the cholesterol oxidation rate of individual enzyme molecules were detected.
    • The study successfully distinguished static and dynamic disorder in reaction rates, which are typically indistinguishable in bulk measurements.
    • Evidence for a molecular memory phenomenon was observed, linked to slow protein conformational fluctuations affecting FAD spectral properties.

    Conclusions:

    • Single-molecule analysis provides unprecedented resolution for studying enzyme kinetics and heterogeneity.
    • Cholesterol oxidase exhibits complex dynamics, including slow conformational fluctuations that influence its catalytic activity.
    • The findings highlight the importance of protein dynamics in enzymatic function and suggest a non-independent nature of sequential turnovers due to molecular memory.