A cytochrome P450 monooxygenase that primarily catalyzes the epoxidation of 11,12 and 14,15 double bonds of (5Z,8Z,11Z,14Z)-eicosatetraenoic acid (arachidonate) forming 11,12- and 14,15-epoxyeicosatrienoic acids (11,12- and 14,15-EET) regioisomers. Mechanistically, uses molecular oxygen inserting one oxygen atom into a substrate, and reducing the second into a water molecule, with two electrons provided by NADPH via cytochrome P450 reductase (CPR; NADPH--hemoprotein reductase). an organic molecule + O2 + reduced [NADPH--hemoprotein reductase] = an alcohol + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] (5Z,8Z,11Z,14Z)-eicosatetraenoate + O2 + reduced [NADPH--hemoprotein reductase] = 11,12-epoxy-(5Z,8Z,14Z)-eicosatrienoate + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] (5Z,8Z,11Z,14Z)-eicosatetraenoate + O2 + reduced [NADPH--hemoprotein reductase] = 14,15-epoxy-(5Z,8Z,11Z)-eicosatrienoate + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] Lipid metabolism; arachidonate metabolism. Liver. P450 can be induced to high levels in liver and other tissues by various foreign compounds, including drugs, pesticides, and carcinogens. Belongs to the cytochrome P450 family.