Carotenoid-protein complexes were extracted with 0.6 M ammonium sulfate from the exoskeleton of crab, Sesarma haematocheir, from the epidermis of starfish, Asterina spectinitera, and from the ovaries of sea urchin, Hemicentrotus pulcherrimus. These pigmented proteins were salted out by ammonium sulfate fractionation. The absorption spectra at visual region, the electrophoretic behavior on a cellulose acetate film, and the prosthetic group carotenoid composition of the proteins were determined successively.
The results are as follows.
1) A faint red protein of the crab exoakeleton was determined as a carotenoprotein having an absorption maximum in visual region at 455 nm in phosphate buffer pH 7.3. Heated at 100°C for 10 min., it yielded a shift of the absorption maximum to 475 nm accompanied by a decrease in electrophoretic mobility. Carotenoid analysis by silicagel thin-layer chromatography showed the presence of astaxanthin and another xanthophyll component as the prosthetic group of the carotenoprotein.
2) The pigment obtained from the sea urchin ovaries was a kind of lipoprotein with yellow color. The absorption spectrum of the carotenoid-lipoprotein complex was similar to that of the acetone extract from the ovaries. While the heating caused a decrease of electrophoretic mobility of the lipoprotein, the color and absorption maxima remained unchanged. The carotenoid composition of the pigment somewhat resembled that of the whole extract with acetone from the ovaries.
3) In the starfish, the pigmented protein was separately extracted from the blue and the red parts of epidermis. The carotenoproteins extracted from both parts were a mixture of various pigmented carotenoproteins. The carotenoproteins in the red epidermis showed the absorption maxima at 400 and 600 nm. And those extracted from the blue epidermis showed absorption maxima at 400, 600, 640 nm with small peaks at 475, 515 nm. However, after heating these carotenoprotein became undifferentiated in absorption spectra and electrophoretic behavior. Carotenoid analysis showed the presence of astaxanthin and two other unidentified xanthophylls as the prosthetic group of these carotenoproteins.