A cytochrome P450 monooxygenase involved in the metabolism of endocannabinoids and steroids (PubMed:21289075, PubMed:12865317). 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 (NADPH--hemoprotein reductase). Catalyzes the epoxidation of double bonds of arachidonoylethanolamide (anandamide) to 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acid ethanolamides (EpETrE-EAs), potentially modulating endocannabinoid system signaling (PubMed:21289075). Hydroxylates steroid hormones, including testosterone at C-16 and estrogens at C-2 (PubMed:21289075, PubMed:12865317). Plays a role in the oxidative metabolism of xenobiotics, including plant lipids and drugs (PubMed:11695850, PubMed:22909231). Acts as a 1,4-cineole 2-exo-monooxygenase (PubMed:11695850). Allele 2B6*9: Has low affinity for anandamide and can only produce 11,12 EpETrE-EAs. N-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-ethanolamine + O2 + reduced [NADPH--hemoprotein reductase] = H(+) + H2O + N-(14,15-epoxy-5Z,8Z,11Z-eicosatrienoyl)-ethanolamine + oxidized [NADPH--hemoprotein reductase] N-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-ethanolamine + O2 + reduced [NADPH--hemoprotein reductase] = H(+) + H2O + N-(11,12-epoxy-5Z,8Z,14Z-eicosatrienoyl)-ethanolamine + oxidized [NADPH--hemoprotein reductase] N-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-ethanolamine + O2 + reduced [NADPH--hemoprotein reductase] = H(+) + H2O + N-(8,9-epoxy-5Z,11Z,14Z-eicosatrienoyl)-ethanolamine + oxidized [NADPH--hemoprotein reductase] O2 + reduced [NADPH--hemoprotein reductase] + testosterone = 16alpha,17beta-dihydroxyandrost-4-en-3-one + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] O2 + reduced [NADPH--hemoprotein reductase] + testosterone = 16beta,17beta-dihydroxyandrost-4-en-3-one + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] 17beta-estradiol + O2 + reduced [NADPH--hemoprotein reductase] = 2-hydroxy-17beta-estradiol + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] estrone + O2 + reduced [NADPH--hemoprotein reductase] = 2-hydroxyestrone + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] 1,4-cineole + O2 + reduced [NADPH--hemoprotein reductase] = 2-exo-hydroxy-1,4-cineole + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] Expressed in liver, lung and heart right ventricle. By phenobarbital. Phosphorylation is accompanied by a decrease in enzyme activity. Variability among CYP2B6 alleles may account for differential metabolism of endogenous steroids and endocannabinoids among individuals. For 16-alpha hydroxylation of testosterone, Vmax/Km values between alleles decrease in the following order: 2B6*1 > 2B6*6 > 2B6*9 > 2B7*4. For 16-beta hydroxylation of testosterone, 2B6*6 has the highest catalytic efficiency. For anandamide metabolism, 2B6*6 and 2B6*9 alleles show significantly lower rates of epoxidation (PubMed:21289075). Genetic variations in CYP2B6 are responsible for poor metabolism of efavirenz and, therefore, susceptibility to efavirenz toxicity in the central nervous system [MIM:614546]. Efavirenz is a non-nucleoside reverse transcriptase inhibitor frequently prescribed with 2 nucleoside reverse transcriptase inhibitors as initial therapy for human immunodeficiency virus (HIV) infection. Up to half of patients treated with efavirenz, experience side effects in the central nervous system, including dizziness, insomnia, impaired concentration, somnolence, and abnormal dreams. Severe depression, aggressive behavior, and paranoid or manic reactions may also occur, depending on efavirenz concentration in the plasma. Patients homozygous for 2B6*6 have significantly higher plasma efavirenz levels when compared to 2B6*6 heterozygous ones (PubMed:15622315, PubMed:15194512, PubMed:20639527). Belongs to the cytochrome P450 family. CYP2B6 alleles