THE DELTA-5-PATHWAY IN STEROID-METABOLISM IN THE SEA STAR ASTERIAS-RUBENS L

1. 1. The △5-pathway in steroid metabolism in Asterias rubens was studied using incubations of pieces of tissue from gonads and pyloric caeca with either cholesterol, pregnenolone, or dehydroepiandrosterone. 2. 2. This pathway, known from vertebrates, also exists in the sea star. 3. 3. Conversion percentages showed large differences among the precursors used. The underlying causes are discussed. 4. 4. Conversion of intermediate △5-steroids into the corresponding △ 4-steroids can take place at (at least) two sites of the △5-pathway. One is at the C21-steroid and one at the C19-steroid level. 5. 5. The biosynthesis of two novel fatty-acyl steroids is reported: viz fatty-acyl pregnenolone and mono-fatty-acyl androstenediol. The physiological function of these esters will be discussed. © 1990.