Hydroxylation and Lyase Activities of Human Cytochrome P450 17A1
Human cytochrome P450 17A1 is a monooxygenase enzyme that catalyzes both the 17a-hydroxylation and 17,20-lyase reactions in the steroid hormone biosynthetic pathway. While only the former function is required for the production of glucocorticoids, both are vital for the synthesis of the sex hormones: androgens and estrogens, which creates a unique issue when targeting the enzyme to treat sex steroid responsive cancers without hindering the production of essential glucocorticoids. Identification of the specific structural regions, peptides and/or amino acids in enzyme that distinguish between the 17a-hydroxylation and 17,20-lyase activities is the primary interest of my investigation. In this structure/function investigation, I will conduct kinetic and structural analyses on clinically reported and naturally evolved P450 17A1 variants. The methods employed will include substrate binding analysis, steady-state and rapid reaction kinetic measurements (e.g. stopped-flow, rapid-quench), crystallography, etc. Additionally, I will examine the mechanism by which the lyase-specific inhibitor, Orteronel, impedes only the 17,20-lyase function.