Mechanism of human placental aromatase: a new active site model.

Based on Akhtar's ferric peroxide mechanism and on recent studies in our own laboratory, we present a detailed proposal for aromatase action. This picture can account for the known stereochemical consequences at C-19 observed by others using isotopes of hydrogen and oxygen. The postulated process involves anchoring of the 19-hydroxymethyl and 19-oxo groups at the active site by a glutamate residue, which also serves to activate the 19-oxo group for attack by ferric peroxy species in the third oxidative step.