Highly active in the 15-alpha-hydroxylation of testosterone. Also active in the 15-alpha-hydroxylation of progesterone and androstenedione. Little or no activity on corticosterone, pregnenolone, dehydroepiandrosterone, estradiol or estriol. an organic molecule + O2 + reduced [NADPH--hemoprotein reductase] = an alcohol + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] Kidney and lung. Expressed in liver, with a strong circadian rhythmicity. Circadian expression is regulated by DBP. There are only 11 differences between the sequence of testosterone 15-alpha-hydroxylase and that of coumarin 7-hydroxylase. By site-directed mutagenesis it has been shown that modification of position 209 is sufficient to convert the specificity of the two forms of the enzyme. Belongs to the cytochrome P450 family.