MOLECULAR-CLONING AND EXPRESSION OF CYP2J2, A HUMAN CYTOCHROME-P450 ARACHIDONIC-ACID EPOXYGENASE HIGHLY EXPRESSED IN HEART

A cDNA encoding a human cytochrome P450 arachidonic acid epoxygenase w as isolated from a human liver cDNA library. Sequence analysis reveale d that this 1,876-base pair cDNA contained an open reading frame and e ncoded a new 502-amino acid protein designated CYP2J2. Blot hybridizat ion analysis of RNA prepared from human tissues revealed that CYP2J2 w as highly expressed in the heart. Recombinant CYP2J2 protein was prepa red using the baculovirus expression system and purified to near elect rophoretic homogeneity. The enzyme metabolized arachidonic acid predom inantly via olefin epoxidation to all four regioisomeric cis-epoxyeico satrienoic acids (catalytic turnover 65 pmol of product formed/nmol of cytochrome P450/min at 30 degrees C). Epoxidation of arachidonic acid by CYP2J2 at the 14,15-olefin was highly enantioselective for (14R,15 S)-epoxyeicosatrienoic acid (76% optical purity). Immunoblotting of mi crosomal fractions prepared from human tissues using a polyclonal anti body raised against the recombinant hemoprotein confirmed primary expr ession of CYP2J2 protein in human heart. The in vivo significance of C YP2J2 was suggested by documenting the presence of epoxyeicosatrienoic acids in the human heart using gas chromatography/mass spectroscopy. importantly, the chirality of CYP2J2 products matched that of the epox yeicosatrienoic acid enantiomers present, in vivo, in human heart. We propose that CYP2J2 is one of the enzymes responsible for epoxidation of endogenous arachidonic acid pools in human heart and that epoxyeico satrienoic acids may, therefore, play important functional roles in ca rdiac physiology.