Effects of ethanol and other organic solvents on the kinetic behaviour of purified human placental oestradiol-17 beta-dehydrogenase.

The effects of acetone, ethanol, dimethylsulphoxide, glycerol, and propanediol on the formation of reduced coenzyme in the presence of purified human placental oestradiol dehydrogenase were measured fluorometrically at 10 microM oestradiol-17 beta and 500 microM NAD. Addition of increasing amounts of each solvent except glycerol resulted in an initial increase followed by a decline in rate of the enzyme catalyzed reaction. Glycerol caused a linear decline in rate. A range (0.1-25%, v/v) of ethanol concentrations was tested for its effect upon the Km and Vmax values for oestradiol, NAD, and NADP. Over this range the Km value for NADP remained nearly constant (0.6-0.8 microM). The Km value for NAD increased rapidly with an upward convex shape of the curve (6.6-25 microM), and the Km value for oestradiol with NAD or NADP as cofactor increased slowly with an upward concave shape (6.7-25 microM). With increasing ethanol concentration, the maximum velocity increased, reaching its highest values at 10 and 20% ethanol for NAD and NADP, respectively, and then declined. At the maximum Vmax values for NAD and NADP were, respectively, 165 and 200% the values obtained with 0.1% ethanol.