The in vitro biosynthesis of steroids by the gonad of the cuttlefish (Sepia officinalis L.)

In vitro steroid biosynthesis in the male and female gonads of Sepia officinalis was investigated. Using tritium- and ¹⁴C-labeled precursors, seven enzyme systems were demonstrated: a C_20,22-lyase (cholesterol→pregnenolone), a 3β-hydroxysteroid dehydrogenase-Δ_5?4-isomerase complex (pregnenolone → progesterone; 17α-hydroxypregnenolone → 17α-hydroxyprogesterone; dehydroepiandrosterone → androstenedione), a 17α-hydroxylase (pregnenolone → 17α-hydroxypregnenolone; progesterone → 17α-hydroxyprogesterone), a C_17,20-lyase (17α-hydroxypregnenolone → dehydroepiandrosterone), a 17β-hydroxysteroid dehydrogenase (dehydroepiandrosterone → androstenediol; androstenedione → testosterone; estrone→estradiol-17β), a 20α-ol dehydrogenase (progesterone→20α-dihydroprogesterone), and a 20β-ol dehydrogenase (progesterone→20β-dihydroprogesterone). The yields were rather low (0.01–3%), except when pregnenolone was used (8%). Radioimmunoassay techniques indicate the presence of testosterone in the plasma of the cuttlefish but the absence of estrogens.