Cytochrome form-specific assays

A critical parameter for the development and application of this approach is the use of enzyme-specific assays for the assessment of the catalytic activities of individual enzymes in human liver microsomes. Cytochrome P450 form-specific assays have been developed for in vitro measurement of most human cytochrome P450 forms. Many of these specific assays will be discussed in Section 6. 

N-hydroxy-Trp-P-2. More recently, the metabolism of IQ has been assessed by the same laboratory (Yamazoe et al., 1983). As was found for Trp-P-2, IQ is metabolized to the N-hydroxy derivative. A specific form of purified cytochrome P-450 designated P-448 Ila appears to be responsible for the metabolic activation of IQ. The activity of this N-hydroxy metabolite is calculated to be 5 X 10E5 revertants per nmole. This metabolite is the most mutagenic compound ever tested in the Ames/Salmonella assay, three times more potent than 1,8 dinitropyrene (Rosenkranz et al. 1980). 

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