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Autoxidation of ascorbic acid catalyzed by a semisynthetic enzyme
1Laboratory of Bioorganic Chemistry and Biochemistry, Rockefeller University, New York, New York 10021.
Biopolymers
|January 1, 1990
Summary
A new semisynthetic enzyme, papain-bipyridine 6, was created. This enzyme binds copper and rapidly catalyzes ascorbic acid autoxidation, outperforming a model system.
Area of Science:
- Biochemistry
- Enzyme kinetics
- Coordination chemistry
Background:
- Papain is a cysteine protease.
- Copper ions play roles in biological redox reactions.
- Ascorbic acid is a key biological antioxidant.
Purpose of the Study:
- To create a semisynthetic enzyme by modifying papain.
- To investigate the copper-binding properties of the modified enzyme.
- To evaluate the catalytic activity of the enzyme in ascorbic acid autoxidation.
Main Methods:
- Alkylation of papain's cysteine-25 residue with bipyridine.
- Stoichiometric copper ion binding assays.
- Enzyme kinetics studies of ascorbic acid derivative autoxidation.
Main Results:
- The semisynthetic enzyme 6 was successfully prepared.
- Enzyme 6 stoichiometrically bound copper ions.
- Enzyme 6 catalyzed ascorbic acid derivative autoxidation ~20-fold faster than a model system.
Conclusions:
- Semisynthetic modification of papain yields a functional copper-binding enzyme.
- The modified enzyme exhibits enhanced catalytic activity for ascorbic acid autoxidation.
- This work presents a novel bioinorganic catalyst for redox reactions.