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Biol Chem Hoppe Seyler. 1985 Jan;366(1):23-31.

A new monooxygenase product from 7-ethoxycoumarin and its relation to the O-dealkylation reaction.


The widely used fluorometric microsomal monooxygenase test for 7-ethoxycoumarin O-dealkylation was reinvestigated with regard to other possible hydroxylation products. By HPLC-analysis no beta-hydroxylation of the ethyl group and no 8-hydroxylation could be detected. Only a small percentage of 6-hydroxylation occurred, but as a new major metabolite 7-ethoxy-3-hydroxycoumarin was found in quantities depending on the microsomal preparation used. The ratio of O-dealkylation to 3-hydroxylation varied according to species, induction, buffer and pH, suggesting that different isozymes of cytochrome P450 were involved. The isozyme mainly responsible for 3-hydroxylation exhibited a great dependence on cytochrome b5 as the donor for the second electron. The fluorometric test does not include 3-hydroxylation due to the virtual absence of an emission spectrum above 450 nm.

[Indexed for MEDLINE]

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