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Oxidation of reduced cucumber ascorbate oxidase.
Biochemical and Biophysical Research Communications
|September 16, 1985
Summary
Cucumber ascorbate oxidase (1.10.3.3) reoxidation reveals distinct copper site reactivity. Specific type I and type II copper sites reoxidize faster, contributing to L-ascorbate oxidation.
Area of Science:
- Biochemistry
- Enzymology
- Spectroscopy
Background:
- Ascorbate oxidase (1.10.3.3) is a multi-copper enzyme crucial for L-ascorbate oxidation.
- Understanding the reoxidation kinetics of its active site is key to elucidating its catalytic mechanism.
Purpose of the Study:
- To investigate the reoxidation process of reduced cucumber ascorbate oxidase by dioxygen.
- To differentiate the reoxidation rates of various copper sites within the enzyme.
Main Methods:
- Absorption spectroscopy
- Circular dichroic (CD) spectroscopy
- Electron paramagnetic resonance (EPR) spectroscopy
Main Results:
- Differential reoxidation rates were observed for the copper sites.
- One type I copper and the type II copper reoxidized more rapidly than other type I coppers.
- The active site is proposed to contain one type I, one type II, and a pair of type III coppers, similar to laccase and ceruloplasmin.
Conclusions:
- The reoxidation kinetics provide insights into the functional roles of different copper sites.
- All identified copper centers, including remaining type I and type III coppers, contribute to L-ascorbate oxidation.