TABLE 3

Kinetic parameters of DHEA-3S 16α-hydroxylation by CYP3As and CYP3A chimeras expressed in TN-5 cells

Maximal velocity (Vmax) and apparent affinity constant (Km) were determined by Lineweaver-Burk plot analysis. DHEA-3S 16α-hydroxylation was determined in three experiments over a DHEA concentration range of 2.5 to 100 μM.


System

Km

Vmax

Vmax/Km
μM nmol/nmol P450/min ml/nmol P450/min
CYP3A7 18.5 6.5 0.35
CYP3A4 106.2 0.9 0.01
CYP3A7(279)/4 26.4 13.5 0.51
CYP3A4(279)/7 134.6 1.1 0.01
CYP3A4(209)/7 23.4 3.6 0.15
CYP3A4(109)/7
20.7
4.6
0.22