Table 3
TroughPeakΔAmaxKDSpin Change
nm cm−1μM−1 μM %
WT4203900.0488.338
(0.002)(0.6)
I120W4223890.0503.539
(0.000)(0.3)
T309F4263890.04216.433
(0.002)(3.0)
I369W4273900.01418.011
(0.000)(4.1)

Midazolam dissociation constant, maximal absorbance change and percent spin-state change on enzyme-substrate complex formation for the wild-type CYP3A4 and selected mutants. An extinction coefficient of 126 mM−1 cm−1 has been used to calculate the percentage spin change due to MDZ binding with the enzyme (Harlow and Halpert, 1998). The values in parentheses show the average deviation obtained from the fit of the equation ΔA = ΔA max S/K D + S, where K D is the dissociation constant and ΔA and ΔA max are the change in absorbance at a particular substrate concentration (S) and at saturating substrate concentration, respectively.