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Updated: Feb 11, 2026
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Application of Stopped-flow Kinetics Methods to Investigate the Mechanism of Action of a DNA Repair Protein
Published on: March 31, 2010
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A Random-Sequential Kinetic Mechanism for Polysaccharide Monooxygenases.
John A Hangasky1, Michael A Marletta1,2,3
1California Institute for Quantitative Biosciences (QB3) , University of California , Berkeley , California 94720 , United States.
Biochemistry
|April 24, 2018
Summary
Polysaccharide monooxygenases (PMOs) use copper and oxygen to break down polysaccharides. This study reveals their random-sequential mechanism and pH-dependent activity, crucial for understanding glycosidic bond cleavage.
Area of Science:
- Biochemistry
- Enzymology
- Structural Biology
Background:
- Polysaccharide monooxygenases (PMOs) are copper enzymes that hydroxylate polysaccharides, cleaving glycosidic bonds.
- The detailed catalytic mechanism of PMOs, particularly their interaction with oxygen and substrates, remains largely unelucidated.
Purpose of the Study:
- To investigate the kinetic mechanism of oxygen-dependent cellohexaose oxidation by the polysaccharide monooxygenase MtPMO9E.
- To determine the influence of substrate concentration and pH on PMO activity and elucidate key mechanistic steps.
Main Methods:
- Steady-state kinetics assays were employed to analyze cellohexaose oxidation by MtPMO9E.
- Inhibition studies using carbon monoxide and determination of dissociation constants (KD) for Glc6 were performed for both Cu(I) and Cu(II) enzyme forms.
Main Results:
- Kinetic analysis indicated a random-sequential mechanism involving a ternary complex (ES-O2).
- Optimal activity for MtPMO9E was observed between pH 6.00 and 7.00, with activity decreasing at lower pH due to protonation (p Ka of 5.10).
Conclusions:
- PMOs operate via a random-sequential kinetic mechanism.
- A general base, likely protonated at low pH, is essential for PMO catalytic turnover, providing insights into the initial chemical steps.
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