The formation of biologically active steroid hormones is significantly influenced by the motrochondrial cytochrome P450 enzyme, chrolesterol side-chain cleavage. CYP11A1 functions in catalyzing the first step of steroid biosynthesis under modulation of cAMP.It ia also known as cytochrome P450C11A1, cytochrome P450scc and cytochrome P450, subfamily XIA. Expression of CYP11A1 has been a useful tool for monitoring the differentiation state of cells from varius endocrine tissues. Identification of CYP11A1 expression by 13363-1-AP detected a ~45kd band in human placenta, with respect to the reported band at 49-52kd by Roby, et al and Durkee, et al.