Studies on the activity of 17 beta-hydroxysteroid dehydrogenase in human adipose tissue

The activity of 17 beta-hydroxysteroid dehydrogenase has been investigated in human subcutaneous adipose tissue. Using oestrone as substrate, oestradiol formation was linear with time and the concentration of protein in the tissue homogenate. The optimum pH was 8.0 and the Km for oestrone was 2.5 x 10(-6) M. With NADH, the production of oestradiol was about 30% of that with NADPH. Oestradiol was also a substrate for the enzyme although under the experimental conditions used reduction of oestrone appeared to be favoured in adipose tissue. In the presence of progesterone (31.8 x 10(-6) M) the Km for oestrone was increased fivefold.