Purification and Characterization of Recombinant Human Neutrophil Leukotriene B4ω-Hydroxylase (Cytochrome P450 4F3)

Recombinant human neutrophil leukotriene B4(LTB4) ω-hydroxylase (cytochrome P450 4F3) has been purified to a specific content of 14.8 nmol of P450/mg of protein from yeast cells. The purified enzyme was homogenous as judged from the SDS–PAGE, with an apparent molecular weight of 55 kDa. The enzyme catalyzed the ω-hydroxylation of LTB4with aKmof 0.64 μM andVmaxof 34 nmol/min/nmol of P450 in the presence of rabbit hepatic NADPH–P450 reductase and cytochromeb5. Furthermore, various eicosanoids such as 20-hydroxy-LTB4, 6-trans-LTB4, lipoxin A4, lipoxin B4, 5-HETE and 12-HETE, and 12-hydroxy-stearate and 12-hydroxy-oleate were efficiently ω-hydroxylated, although theirKmvalues were much higher than that of LTB4. In contrast, no activity was detected toward laurate, palmitate, arachidonate, 15-HETE, prostaglandin A1, and prostaglandin E1, all of which are excellent substrates for the CYP4A fatty acid ω-hydroxylases. This is the first time human neutrophil LTB4ω-hydroxylase has been isolated in a highly purified state and characterized especially with respect to its substrate specificity.