Ovorubin, a Chromoprotein from the Eggs of the Gastropod Mollusc Pomacea canaliculata

The eggs of Pomacea canaliculata australis (d’Orbigny), an amphibious freshwater prosobranch snail, have, as the most important nitrogenous constituent of the jelly surrounding the ovum, a red glycoprotein with a carotenoid prosthetic group. This protein, to which the name ovorubin has been given, has a high stability to denaturation by heat and by adsorption at interfaces. It is partially utilized during development of the ovum, although about two-thirds of the original ovorubin content of the egg is found in the visceral hump of the newly hatched animal. The carotenoid component is probably an ester or ether of astaxanthin, highly labile to alkali in the cold. The minimum molecular weight, calculated from the carotenoid content, lies in the region of 330 000. The carbohydrate component represents about 20% of the molecule. The carotenoid and the glycoprotein may readily be separated and recombined. Experiments on the apo-glycoprotein and the reconstituted caroteno-protein indicate that the carotenoid stabilizes the native configuration of the protein structure. It is suggested that stabilization of the configurations of protein molecules may be one of the roles of carotenoids in nature.