title: Toxicity of melanin-free ink of Sepia officinalis to transformed cell lines: identification of the active factor as tyrosinase.
abstract: The melanin-free ink of the cephalopod Sepia officinalis is shown to contain a heat labile proteinaceous component toxic to a variety of cell lines, including PC12 cells. Gel filtration chromatography indicated that the toxic component was concentrated in those fractions eluted at a molecular weight higher than 100 kDa and exhibiting the highest tyrosinase activity. SDS-PAGE analysis of the active fractions displayed a single major band migrating at an approximate molecular weight of 100 kDa, identical with that of the single tyrosinase band in the melanin-free ink. These data unambiguously demonstrated the identity of the toxic component with tyrosinase. Treatment of purified Sepia as well as of mushroom tyrosinase with an immobilized version of proteinase K resulted in a parallel loss of tyrosinase activity and cytotoxicity. Sepia apotyrosinase was ineffective in inducing cytotoxicity in PC12 cells. Purified Sepia tyrosinase was found to induce a significant increase in caspase 3 activity in PC12 cells, leading eventually to an irreversible apoptotic process. Overall, these results disclose a hitherto unrecognized property of tyrosinase that may lead to a reappraisal of its biological significance beyond that of a mere pigment producing enzyme.
authors.affiliation: Institute of Food Science, National Research Council, Avellino, Italy.
authors.forename: Gian Luigi
authors.initials: GL
authors.lastname: Russo
authors.forename: Elio
authors.initials: E
authors.lastname: De Nisco
authors.forename: Gabriella
authors.initials: G
authors.lastname: Fiore
authors.forename: Paola
authors.initials: P
authors.lastname: Di Donato
authors.forename: Marco
authors.initials: M
authors.lastname: d'Ischia
authors.forename: Anna
authors.initials: A
authors.lastname: Palumbo
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D018938:Caco-2 Cells; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002461:Cell Line, Transformed; D019286:Endopeptidase K; D006801:Humans; D007281:Ink; D019169:Jurkat Cells; D008543:Melanins / Q000302:isolation & purification; D008974:Mollusca / Q000201:enzymology*; D014442:Monophenol Monooxygenase / Q000302:isolation & purification / Q000633:toxicity*; D016716:PC12 Cells; D051381:Rats
chemical_list: D008543:Melanins; D014442:Monophenol Monooxygenase; D019286:Endopeptidase K; C505407:CASP3 protein, human; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases