Induction, purification, and characterization of cytochrome P450IIE.

Publisher Summary This chapter discusses the induction, purification, and characterization of cytochrome P450IIE. Most cytochromes P450 are inducible by, and catalyze the oxidation of, rather large hydrophobic molecules. However, it was discovered that many small water-soluble molecules are inducers and substrates of a specific form of cytochrome P450. The genes of P450IIE1 have been cloned and characterized in rats, rabbits, and humans. Similar enzymes, such as the low K m form of N-nitrosodimethylamine (NDMA) demethylase, have been shown to exist in mice, guinea pigs, and hamsters based on immunoinhibition of specific catalytic activity. Nevertheless, the final designation of these enzymes as P450IIE1 should await the characterization of their gene sequences. Acetone-induced microsomes are a convenient source for the isolation of P450IIE1. The NDMA demethylase assay has been extensively used in laboratories. At low substrate concentrations, P450IIE1 is the only known P450 isozyme showing substantial activity.