Animal carotenoids 15. Carotenoid distribution and carotenoprotein of Asterias rubens.

A clear differentiation in localization according to functional groups in the carotenoids of the starfish, Asterias rubens, is reported. Only the free alpha-ketols, 7,8,7',8'-tetradehydroastaxanthin, 7,8-didehydroastaxanthin and astaxanthin, are present in the purified carotenoprotein. A post mortem liberated slime contained beta,beta-carotene, free and esterified alloxanthin and esterified alpha-ketols. Evidence suggesting the existence of an alloxanthin protein complex was obtained. The carotenoprotein, asteriarubin, accounts for approx. 10% of the protein extracted by low salt dialysis from the purple-blue part of the top skin of A. rubens and exhibits an absorbance maximum at 554 nm in buffer solution. Asteriarubin is a glycoprotein with an equivalent Stoke's radius corresponding to that of globular proteins of molecular weight 8--10 10(4) and contains 20 microgram carotenoid per mg asteriarubin. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of purified asteriarubin disclosed two major components, one of which is a glycopeptide.