Cytochromes P450 are a group of heme-thiolate monooxygenases. Catalyzes the omega-hydroxylation of LTB4 (By similarity). leukotriene B4 + O2 + reduced [NADPH--hemoprotein reductase] = 20-hydroxy-leukotriene B4 + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] Lipid metabolism; leukotriene B4 degradation. Belongs to the cytochrome P450 family.