Skip to Main Content
Table 1.

NADPH-supported E2 hydroxylation activities of human CYP1A1 variants

2-OH-estradiol
4-OH-estradiol
6α-OH-estradiol
15α-OH-estradiol
VmaxKmVmax/KmVmaxKmVmax/KmVmaxKmVmax/KmVmaxKmVmax/Km
CYP1A1.1 0.6 ± 0.1 9.5 ± 4.6 0.063 0.02 ± 0.002 11.8 ± 4.8 0.002 3.6 ± 0.8 79 ± 26 0.046 0.9 ± 0.1 19.6 ± 7.3 0.046 
CYP1A1.2 3.3 ± 0.3 9.2 ± 2.3 0.359 0.08 ± 0.02 12.9 ± 6.5 0.006 1.3 ± 0.2 21.7 ± 6.2 0.060 9.3 ± 0.6 86 ± 8.0 0.108 
CYP1A1.4 0.3 ± 0.03 9.8 ± 3.2 0.031 0.02 ± 0.002 12.3 ± 3.6 0.002 0.9 ± 0.1 18.6 ± 2.9 0.048 3.7 ± 0.6 89 ± 20 0.042 
2-OH-estradiol
4-OH-estradiol
6α-OH-estradiol
15α-OH-estradiol
VmaxKmVmax/KmVmaxKmVmax/KmVmaxKmVmax/KmVmaxKmVmax/Km
CYP1A1.1 0.6 ± 0.1 9.5 ± 4.6 0.063 0.02 ± 0.002 11.8 ± 4.8 0.002 3.6 ± 0.8 79 ± 26 0.046 0.9 ± 0.1 19.6 ± 7.3 0.046 
CYP1A1.2 3.3 ± 0.3 9.2 ± 2.3 0.359 0.08 ± 0.02 12.9 ± 6.5 0.006 1.3 ± 0.2 21.7 ± 6.2 0.060 9.3 ± 0.6 86 ± 8.0 0.108 
CYP1A1.4 0.3 ± 0.03 9.8 ± 3.2 0.031 0.02 ± 0.002 12.3 ± 3.6 0.002 0.9 ± 0.1 18.6 ± 2.9 0.048 3.7 ± 0.6 89 ± 20 0.042 

NOTE: NADPH-supported reactions were done in a reconstituted system consisting of purified human CYP1A1 variant, purified human P450 reductase and insect control microsomes. The final concentrations for determination of activities were 80 nmol/L, 400 nmol/L, and 320 μg/mL for CYP1A1, P450 reductase, and control microsomes, respectively. Formation of hydroxylated products was determined using HPLC and kinetic analyses were done by nonlinear regression as described under Materials and Methods.

Vmax data are given in picomoles of product per minute/picomoles of CYP1A1, Km data are in micromoles per liter, and catalytic efficiencies Vmax/Km are expressed in liter/micromoles per minute. Data represent mean ± SE as determined by nonlinear regression using software described under Materials and Methods.

Close Modal

or Create an Account

Close Modal
Close Modal