Electron acceptor function of O2 in radical N-demethylation reactions catalyzed by hemeproteins |
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Authors: | Patricia L Ashley Debra K Davis Brenda Walker Griffin |
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Institution: | Biochemistry Dept. The University of Texas Health Science Center at Dallas Dallas, Texas 75235 USA |
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Abstract: | In aerobic solutions, O2 consumption correlated well with N-demethylation of N,N-dimethyl--toluidine catalyzed by horseradish peroxidase, in the presence or absence of H2O2. In the absence of added H2O2, superoxide dismutase stimulated, and catalase inhibited, both reactions; in the presence of H2O2, argon inhibition of formaldehyde production increased with increasing concentration of horseradish peroxidase. These results provide evidence for competing reactions of the enzymatically-generated substrate radical: oxidation by O2 increases formaldehyde production, while radical dimerization decreases the yield of this product. Implications of these findings for similar reactions catalyzed by microsomal cytochrome P-450 are suggested. |
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