BACULOVIRUS-MEDIATED HIGH-LEVEL EXPRESSION OF HUMAN PLACENTAL AROMATASE (CYP19A1)

An efficient expression system for a cDNA clone of human placental aro matase has been developed using the baculovirus expression system in T N5 (Tricoplusia ni) cells. The protein was expressed at high levels, w ith specific aromatase activity and specific P450 content comparable t o that found in human placental microsomes. To achieve these high leve ls of activity, hemin had to be added to the cultures of infected cell s and NADPH-cytochrome P450 reductase had to be included in the assay buffer. The spectral properties of ligand bound forms of the baculovir us expressed aromatase were very similar to those exhibited by the sam e ligand bound forms of the enzyme purified from placental microsomes. This expression system appears to be a suitable source for the purifi cation of milligram quantifies of recombinant aromatase. (C) 1994 Acad emic Press, Inc.