Pregnenolone-7beta-hydroxylating activity of human cytochrome P450-1A1.
In many human and murine tissues, both pregnenolone and dehydroepiandrosterone are hydroxylated at the 7alpha and 7beta positions by a cytochrome P450-containing microsomal complex. The 7alpha- and 7beta-hydroxysteroids produced were shown to activate an immune response in mice. Based upon identification by crystallization to constant specific activity and gas chromatography-mass spectrometry analysis, we ascertained that a yeast-expressed human cytochrome P450-1A1 was able to 7beta-hydroxylate pregnenolone (K(M) from 3.2 +/- 0.5 to 4.1 +/- 0.4 microM, turnover number from 117 +/- 15 to 135 +/- 13 pmol/min/nmol of cytochrome P450-1A1). The other human cytochromes P450 tested did not produce identifiable quantities of 7alpha- or 7beta-hydroxylated derivatives of pregnenolone or dehydroepiandrosterone. These findings indicate that cytochrome P450-1A1 involvement in the 7beta-hydroxylation of pregnenolone may contribute to the production of the 7-hydroxylated steroids necessary for activation of the immune defences.
Doostzadeh
J
J
Laboratoire de Biotechnologie, Conservatoire National des Arts et Métiers, Paris, France.
Flinois
J P
JP
Beaune
P
P
Morfin
R
R
D002849:Chromatography, Gas / Q000379:methods; D003460:Crystallization; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D003687:Dehydroepiandrosterone / Q000378:metabolism; D006801:Humans; D006900:Hydroxylation; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D013058:Mass Spectrometry / Q000379:methods; D008861:Microsomes / Q000378:metabolism; D011284:Pregnenolone / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015003:Yeasts / Q000235:genetics
D011994:Recombinant Proteins; D003687:Dehydroepiandrosterone; D011284:Pregnenolone; D003577:Cytochrome P-450 Enzyme System; D019363:Cytochrome P-450 CYP1A1