Leukotriene-B omega-hydroxylase 2 is an enzyme that in humans is encoded by the CYP4F3gene. CYP4F3 encodes two distinctenzymes, CYP4F3A and CYP4F3B, which originate from the alternative splicing of a single pre-mRNA precursor molecule; selection of either isoform is tissue-specific with CYP3F3A being expressed mostly in leukocytes and CYP4F3B mostly in the liver.
Function
The cytochrome P450 proteins are monooxygenases which catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids, fatty acids and other lipids. CYP4F3 actually encodes two splice-variants, CYP4F3A and CYP4F3B, of the cytochrome P450 superfamily of enzymes. The gene is part of a cluster of cytochrome P450 genes on chromosome 19. Another member of this family, CYP4F8, is approximately 18 kb away. Both variants localize on the endoplasmic reticulum and metabolize leukotriene B4 and very likely 5-hydroxyeicosatetraenoic acid, 5-oxo-eicosatetraenoic acid, and 12-hydroxyeicosatetraenoic acid by an omega oxidation reaction, i.e. by adding a hydroxyl residue to their terminal carbon. This addition starts the process of inactivating and degrading all of these well-known mediators of inflammation and/or allergy. CYP3FA is the major enzyme accomplishing these omega oxidations in leukocytes. The hydroxylation-induced inactivation of these mediators, perhaps particularly of leukotriene B4, may underlie the proposed roles of these cytochromes in dampening inflammatory responses as well as the reported associations of certain CYP4F3 single nucleotide variants with human Krohn's disease. CYP4F3A and/or CYP43B also omega oxidize arachidonic acid to 20-Hydroxyeicosatetraenoic acid as well as epoxyeicosatrienoic acids to 20-hydroxy-EETs. 20-HETE regulates blood flow, vascularization, blood pressure, and kidney tubule absorption of ions in rodents and possibly humans; it has also been proposed to be involved in regulating the growth of various types of human cancers. EETS have a similar set of regulatory functions but often act in a manner opposite to 20-HETE ; since, however, the activities of the 20-HEETs have not been well-defined, the function of EET omega oxidation is unclear.
