Carotenoproteins in Invertebrates

Abstract

SUMMARY True carotenoproteins are defined as complexes in which a carotenoid and a protein are in stoichiometric combination. Very few carotenoproteins have been purified, but their presence in extracts may often be presumed from spectroscopic evidence. Carotenoids have been found in stoichiometric association with simple proteins, lipoproteins and glycoproteins. Many lipoproteins also occur in which carotenoids form part of the lipid prosthetic group. Although the relationship between the carotenoid and the remainder of the complex may in these cases not appear to be stoichiometric, it often shows some evidence of selectivity. Carotenoproteins are widely distributed among the invertebrate phyla. They are found mainly in exoskeleton or ectoderm and in eggs and ovaries. Their isolation by standard techniques of protein chemistry is facilitated by their characteristic spectral properties. The ease with which carotenoid prosthetic groups are removed from apoproteins suggests that covalent linkages are not involved in the complex formation. The union of carotenoid with apoprotein has been shown, in at least two cases, to stabilize the carotenoid against photo‐oxidation and the protein against denaturative changes of tertiary structure. In crustacyanin, the carapace pigment of the lobster, there is clear evidence that the carotenoid is responsible for establishing the very complex quaternary structure. Only astaxanthin, astaxanthin esters and canthaxanthin have been unequivocally identified as carotenoid prosthetic groups of true carotenoproteins. Experiments in the specificity of interaction of a series of carotenoids with the apoprotein of crustacyanin have indicated the requirement of one or both of the 4‐ and 4′‐keto groups of the carotenoid for interaction with the protein. It is suggested that, at least in this case, the carotenoid‐protein interaction might occur between carotenoid keto groups and basic residues of the protein in such a way as to provide a lock on the tertiary configuration. Carotenoproteins may participate in a variety of functions including protective coloration, photosensitivity, electron transport and enzymic activity. They appear, furthermore, to play some part in development.

Interaction of Lutein with Ovalbumin and Other Proteins: Association and Acquisition of Novel Optical Activity

“…Concentration of lutein was determined spectrophotometrically assuming Et~bm at 446 nm in ethanol to be 2344 and that at 384 nm in aqueous solutions of complexes in 0.1 M sodium phosphate buffer, pH 7.0, to be 1470, respectively.…”

Photoprotection by carotenoid pigments in the copepod Diaptomus nevadensis.

“…While many hypotheses have been forwarded to explain this phenomenon, none had up to the present time been proven (8,9). One of the more plausible of these explanations first proposed by Griffiths et al (10) suggests that the carotenoids protect the animals from potentially damaging, visible wave lengths of light.…”

Effects of Season, Size and Parasitism by the Acanthocephalan, Profilicollis altmani, on the Carotenoid Concentration and Composition of the Pacific Mole Crab, Emerita analoga

“…The opposite may be true for beta-carotene in ovarian tissue and egg, and likewise for astaxanthin in carapace. In these tissues, select carotenoids predominate and seem to serve a specific function, for instance cryptic coloration by use of astaxanthin bound to crustacyanin and reproductive needs by protecting developing embryos with antioxidants in the form of beta-carotene (Wade et al 2009, Cheesman et al 1967, Miki et al 1994.The purpose of high concentrations of astaxanthin and canthaxathin in esophageal tissue is less clear. Canthaxanthin is thought to be a metabolic intermediate of astaxanthin in some crustaceans, so it is less surprising to find the two existing together in the same tissue.…”

“…The compounds responsible for this pigmentation appear to be carotenoids derived from host tissue. Two studies have shown that the predominant carotenoid of cystacanths infecting Gammarus pulex is esterified astaxanthin (Cheesman et al 1967 andGaillard et al 2004). In many acanthocephalans, a single major carotenoid is detected rather than a mixture of pigments.…”