Digestion by pepsin releases biologically active chromopeptides from C-phycocyanin, a blue-colored biliprotein of microalga Spirulina

J Proteomics. 2016 Sep 16;147:132-139. doi: 10.1016/j.jprot.2016.03.043. Epub 2016 Apr 13.


C-phycocyanin, the major protein of cyanobacteria Spirulina, possesses significant antioxidant, anti-cancer, anti-inflammatory and immunomodulatory effects, ascribed to covalently attached linear tetrapyrrole chromophore phycocyanobilin. There are no literature data about structure and biological activities of released peptides with bound chromophore in C-phycocyanin digest. This study aims to identify chromopeptides obtained after pepsin digestion of C-phycocyanin and to examine their bioactivities. C-phycocyanin is rapidly digested by pepsin in simulated gastric fluid. The structure of released chromopeptides was analyzed by high resolution tandem mass spectrometry and peptides varying in size from 2 to 13 amino acid residues were identified in both subunits of C-phycocyanin. Following separation by HPLC, chromopeptides were analyzed for potential bioactivities. It was shown that all five chromopeptide fractions have significant antioxidant and metal-chelating activities and show cytotoxic effect on human cervical adenocarcinoma and epithelial colonic cancer cell lines. In addition, chromopeptides protect human erythrocytes from free radical-induced hemolysis in antioxidative capacity-dependant manner. There was a positive correlation between antioxidative potency and other biological activities of chromopeptides. Digestion by pepsin releases biologically active chromopeptides from C-phycocyanin whose activity is mostly related to the antioxidative potency provided by chromophore.

Keywords: Bioactivity; C-phycocyanin; Digestibility; Peptides; Phycocyanobilin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antioxidants
  • Cell Line, Tumor
  • Cells, Cultured
  • Colonic Neoplasms / drug therapy
  • Color
  • Erythrocytes / drug effects
  • Female
  • Hemolysis / drug effects
  • Humans
  • Pepsin A / metabolism*
  • Peptides / metabolism
  • Peptides / pharmacology*
  • Peptides / therapeutic use
  • Phycocyanin / metabolism*
  • Spirulina / chemistry*
  • Uterine Cervical Neoplasms / drug therapy


  • Antioxidants
  • Peptides
  • Phycocyanin
  • Pepsin A