Olfactory-specific cytochrome P-450 (P-450olf1; IIG1). Gene structure and developmental regulation.

The olfactory neuroepithelium is the principal site of interaction for airborne molecules, mainly odorants, in the organism. The presence of an active cytochrome P-450-dependent oxidative metabolism in this tissue has not yet been studied as well as the hepatic cytochrome P-450-dependent oxidations. In this report, we describe cytochrome P-450olf1 (IIG1), a P-450 gene expressed at high levels uniquely in the olfactory epithelium. By Southern analysis and genomic DNA cloning, we demonstrate that a single copy of the P-450olf1 gene is present in the rat genome and contains 9 exons. We conclude that rat P-450IIG1 is a single gene subfamily. P-450olf1 gene expression was activated after birth in both male and female Sprague-Dawley rats and remained active in adult olfactory epithelium. A first maximum level of expression was reached around postnatal day 21. The coincidence between the temporal gene activation of P-450olf1 and the postnatal increase in the sensitivity of olfactory response to odorants is consistent with a potential role of this enzyme in olfactory function.