Carotenoid-protein complexes.

This chapter provides an updated report of carotenoprotein-related research. Very few carotenoproteins have been purified; however, their presence in aqueous extracts may be indicated by spectroscopic evidence. Carotenoproteins have been isolated, purified, and characterized from the ectoderm, exoskeleton, eggs, and ovaries of marine invertebrates, especially crustaceans. Water-soluble and detergent-soluble carotenoid-protein complexes have also been isolated from the cytoplasmic membrane of some cyanobacteria, Mangifera indica, and carrots. Recently, we have been able to partially purify a beta-carotene-protein complex from fresh livers of rats fed beta-carotene. Studies are currently in progress to purify and characterize the protein. This is the first successful isolation of a vertebrate carotenoprotein. The isolation of carotenoproteins is generally by standard techniques of protein chemistry. Purification, crystallization of the complex, and reconstitution of apoprotein and carotenoid components have been achieved for some crustacean carotenoproteins. The complex is very sensitive to bright light and to temperatures above that of refrigeration. However, it is best preserved in solutions of high ionic strength or as a precipitate in strong ammonium sulfate solutions.