Sterol biosynthesis in the echinoderm Asterias rubens.
1. [2(-14)C]Mevalonic acid injected into the echinoderm Asterias rubens (Class Asteroidea) was effectively incorporated into the non-saponifiable lipid. 2. The most extensively labelled compounds were squalene and the 4,4-dimethyl sterols with much lower incorporations into the 4alpha-monomethyl and 4-demethyl sterol fractions. 3. Labelled compounds identified were squalene, lanosterol, 4,4-dimethyl-5alpha-cholesta-8,24-dien-3beta-ol and 4alpha-methyl-5alpha-cholest-7-en-3beta-ol; these are all intermediates in sterol biosynthesis. 4. The major sterol in A. rubens, 5alpha-cholest-7-en-3beta-ol, was also labelled showing that this echinoderm is capable of sterol biosynthesis de novo. 5. No evidence was obtained for the incorporation of [2(-14)C]mevalonic acid into the C28 and C29 components of the 4-demethyl sterols or 9beta,19-cyclopropane sterols found in A. rubens and it is assumed that these sterols are of dietary origin. 6. Another starfish Henricia sanguinolenta also incorporated [2(-14)C]mevalonic acid into squalene and lanosterol. 7. Various isolated tissues of A. rubens were all capable of incorporation of [2(-14)C]mevalonic acid into the nonsaponifiable lipid. With the body-wall and stomach tissues radioactivity accumulated in squalene and the 4,4-dimethyl sterols, but with the gonads and pyloric caecae there was a more efficient incorporation of radioactivity into the 4-demethyl sterols, principally 5alpha-cholest-7-en-3beta-ol.
D000818:Animals; D002250:Carbon Radioisotopes; D002782:Cholestenes / Q000378:metabolism; D002784:Cholesterol / Q000096:biosynthesis; D007810:Lanosterol / Q000096:biosynthesis; D008798:Mevalonic Acid / Q000378:metabolism; D013185:Squalene / Q000378:metabolism; D013215:Starfish / Q000378:metabolism*; D013261:Sterols / Q000096:biosynthesis*
D002250:Carbon Radioisotopes; D002782:Cholestenes; D013261:Sterols; D007810:Lanosterol; D013185:Squalene; D002784:Cholesterol; D008798:Mevalonic Acid