Proteolytic Attack of the Chromoproteins of Porphyra by Marine Bacterial Enzymes.

Merkel, Joseph R. (College of Charleston, Charleston, S.C.), Gordon D. Braithwaite, and Henry Kritzler. Proteolytic attack of the chromoproteins of Porphyra by marine bacterial enzymes. J. Bacteriol. 88:974-980. 1964.-Three chromoproteins were isolated from the marine red alga, Porphyra leucosticta (Thuret), and were purified by adsorption chromatography on calcium phosphate gel and by ammonium sulfate fractionation. The algal chromoproteins were subjected to the proteolytic action of cultures of actively growing marine bacteria, marine bacterial culture filtrates, trypsin, and various marine bacterial enzyme preparations. Digestion of the chromoproteins was followed through various incubation intervals by measuring the loss of chromophore color and the increase in either ninhydrin-positive material (570 mmu) or 280-mmu light-absorbing material. There was good correlation between the loss of color and enzymatic hydrolysis of the proteins. this was particularly evident when a marine pseudomonad proteinase preparation was used as the proteolytic agent. In every digestion mixture, phycoerythrin was more resistant to degradation than was phycocyanin or allophycocyanin. Phycoerythrin was also more resistant to heat than was phycocyanin or allophycocyanin.