The enzymatic properties for NADPH-P450 reductase domain of a fusion protein between human cytochrome P450 1A1 and rat NADPH-P450 reductase expressed in Escherichia coli were investigated. The fusion plasmid pCW/1A1OR-expressed E. coli membrane showed high NADPH-cytochrome c reductase activity ($830.1pm 85.8 nmolcdot min^{-1}cdot mg protein^{-1}$), while pCW control vector and P 450 1A1 expression vector pCW/1A1 showed relatively quite low activity ($4.35pm 0.49, 3.27pm 0.50 nmolcdot min^{-1}cdot mg protein^{-1}$, respectively). The kinetic curves for NADPH-cytochrome c reductase followed typical Michaelis-Menten kinetics. The $K_{max}$ and $V_{max}$ for NADPH-dependent reductase activity were $8.24pm 2.61mu $and $817.9pm 60.8 nmolcdot min^{-1}cdot mg protein^{-1}$, respectively, whereas those for cytochrome c-dependent reductase activity were $19.97pm 2.86mu M$ and $1303.5pm 67.1 nmolcdot min^{-1}cdot mg protein^{-1}$. The reductase activities were also compared with those of rat, porcine and human liver microsomes. The activity of pCW/ 1A1OR-expressed E. coli membrane was 15.2-fold higher than that of rat liver microsome. Treatment with benzo(a)pyrene, 7-ethoxyresorufin and $alpha$-naphthofiavone which are known as specific substrates or inhibitor for human P450 1A1 increased NADPH-cytochrome c reductase activity of fusion protein in E. coli membrane dose-dependently. These results demonstrate that the membrane topology of fused enzyme may be important for activity of its NADPH-P450 reductase domain.