RAT TESTIS STEROID SULFATASE .2. KINETIC STUDY

The cleavage of pregnenolone sulfate (Km = 0.3 × 10-5 M/L) by rat testis tissue was demonstrated to be more facile than the cleavages of 5-androsten-17β-ol-3β-sulfate (Km = 0.5 × 10-5 M/L), 17β-estradiol-3-sulfate (Km = 1.2 × 10-5 M/L), estrone sulfate (Km = 2 × 10-5 M/L), and 17β-acetyl-5-androstene-3β-sulfate (Km = 3 × 10-5 M/L) respectively. This ranking is confirmed in comparisons with inhibition studies and previously reported data. The preferred pregnenolone sulfate cleavage is inhibited most efficiently by 5-pregnene-3β, 20α-diol. These findings are consistent with the concept of a single steroid sulfatase enzyme to which either substrates or unconjugated steroid inhibitors bind competitively, to an extent partially determined by substituents at C17 as well as the conformations at C5 and C3. © 1968.