THE STRUCTURE OF THE PHYCOBILINS

The literature concerned with the chemistry of algal biliproteins is surveyed. Amino acid analyses of carefully purified samples of Rand C-phycoerythrin, and of C-phycocyanin were performed. All three are characterised by a high percentage of dibasic and of hydrophobic amino acids. R-, B- and C-phycoerythrins were found to contain methionine as their N-terminal amino acid residue. A proteolytic enzyme preparation was obtained from the blue-green alga Phormidium persicinum. The phycoerythrobilin prosthetic group of R-phycoerythrin was purified and some of its physical and chemical properties determined. The urobilin obtained on isomerization of phycoerythrobilin in concentrated hydrochloric acid was studied, and a number of useful derivatives prepared. It was shown that 12N HCl is required to liberate the native prosthetic group of C-phycocyanin. Two other closely related pigments were isolated from this biliprotein and their physical and chemical properties studied. R-phycocyanin was shown to be a homogeneous chromoprotein containing subunits characteristic of phycoerythrin and of C-phycocyanin. Author