RT Journal Article
SR Electronic
T1 Role of Murine Cytochrome P-450 2F2 in Metabolic Activation of Naphthalene and Metabolism of Other Xenobiotics
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 281
OP 288
VO 290
IS 1
A1 Michael A. Shultz
A1 Prabhakara V. Choudary
A1 Alan R. Buckpitt
YR 1999
UL http://jpet.aspetjournals.org/content/290/1/281.abstract
AB Despite their substantially lower levels relative to hepatic tissue, pulmonary cytochrome P-450 (CYP) monooxygenases play an important role in the metabolic activation of substrates that cause lung injury. The target- and species-selective toxicity of a number of pulmonary toxicants has been attributed to the presence and distribution of activating enzymes with highkcat in target airways of susceptible species. However, experimental demonstration of these concepts and quantitative assessment of the contribution of individual CYP isoforms is lacking. This study was undertaken to characterize the catalytic activities of CYP2F2 with naphthalene, a murine Clara cell toxicant, as well as with other xenobiotics that either undergo metabolic activation to cytotoxic intermediates or that function as “isoform-selective” substrates. Recombinant CYP2F2 was produced using the baculovirus expression vector system in Spodoptera frugiperda andTrichoplusia ni cells, accounting up to ∼20% of the total cellular protein. Incubations containing naphthalene, recombinant CYP2F2, NADPH-cytochrome P-450 oxidoreductase, and NADPH-regenerating system metabolized naphthalene with a high degree of stereoselectivity to 1R,2S-naphthalene oxide (66:1 enantiomeric ratio). The Km andkcat values, along with the specificity constant, for naphthalene metabolism by recombinant CYP2F2 were 3 μM, 104 min−1, and 5.8 × 105M−1 s−1, respectively. Recombinant CYP2F2 also metabolized ethoxyresorufin, pentoxyresorufin,p-nitrophenol, and 1-nitronaphthalene at easily detectable levels. The results from this work suggest that CYP2F2 1) plays a key role in the species- and cell-selective toxicity of naphthalene and 2) efficiently metabolizes a number of other substrates, including the lung toxicant 1-nitronaphthalene. The American Society for Pharmacology and Experimental Therapeutics