The reduction of single-site haem and copper redox proteins by ascorbic acid was studied as a function of pH. Evidence is presented that indicates that the double-deprotonated ascorbate anion, ascorbate2-, is the reducing agent, and the pH-independent second-order rate constants for reduction by this species are given. Investigation of the temperature dependences of these rate constants have yielded the values of the activation parameters (delta H++ and delta S++) for reduction. These values, together with ligand-replacement studies, suggest that ascorbate2- acts as an outer-sphere reductant for these proteins. Reasons to account for the apparent inability of ascorbic acid to reduce the alkaline conformer of mammalian ferricytochrome c are suggested.
Research Article| February 01 1979
The mechanism of reduction of single-site redox proteins by ascorbic acid
Biochem J (1979) 177 (2): 641–648.
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A I Al-Ayash, M T Wilson; The mechanism of reduction of single-site redox proteins by ascorbic acid. Biochem J 1 February 1979; 177 (2): 641–648. doi: https://doi.org/10.1042/bj1770641
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