A cytochrome P450 monooxygenase involved in the metabolism of arachidonic acid and its oxygenated derivatives (PubMed:10486137, PubMed:14634044). 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-ferrihemoprotein reductase). Participates in the conversion of arachidonic acid to omega-hydroxyeicosatetraenoic acid (20-HETE), a signaling molecule acting both as vasoconstrictive and natriuretic with overall effect on arterial blood pressure (PubMed:14634044). May play a role in the oxidative inactivation of eicosanoids, including both pro-inflammatory and anti-inflammatory mediators such as leukotriene B4 (LTB4), lipoxin A4 (LXA4), and several HETEs (PubMed:10486137, PubMed:14634044). (5Z,8Z,11Z,14Z)-eicosatetraenoate + O2 + reduced [NADPH--hemoprotein reductase] = 20-hydroxy-(5Z,8Z,11Z,14Z)-eicosatetraenoate + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] 5-hydroxy-(6E,8Z,11Z,14Z)-eicosatetraenoate + O2 + reduced [NADPH--hemoprotein reductase] = 5,20-dihydroxy-(6E,8Z,11Z,14Z)-eicosatetraenoate + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] 8-hydroxy-(5Z,9E,11Z,14Z)-eicosatetraenoate + O2 + reduced [NADPH--hemoprotein reductase] = 8,20-dihydroxy-(5Z,9E,11Z,14Z)-eicosatetraenoate + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] leukotriene B4 + O2 + reduced [NADPH--hemoprotein reductase] = 20-hydroxy-leukotriene B4 + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] 6-trans-leukotriene B4 + O2 + reduced [NADPH--hemoprotein reductase] = 20-hydroxy-6-trans-leukotriene B4 + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] lipoxin A4 + O2 + reduced [NADPH--hemoprotein reductase] = 20-hydroxy-lipoxin A4 + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] Optimum pH is 7.5. Expressed in liver. Highly expressed in aflatoxin B1-induced hepatic tumors. Belongs to the cytochrome P450 family.