title: Tyrosinases from crustaceans form hexamers.
abstract: Tyrosinases, which are widely distributed among animals, plants and fungi, are involved in many biologically essential functions, including pigmentation, sclerotization, primary immune response and host defence. In the present study, we present a structural and physicochemical characterization of two new tyrosinases from the crustaceans Palinurus elephas (European spiny lobster) and Astacus leptodactylus (freshwater crayfish). In vivo, the purified crustacean tyrosinases occur as hexamers composed of one subunit type with a molecular mass of approx. 71 kDa. The tyrosinase hexamers appear to be similar to the haemocyanins, based on electron microscopy. Thus a careful purification protocol was developed to discriminate clearly between tyrosinases and the closely related haemocyanins. The physicochemical properties of haemocyanins and tyrosinases are different with respect to electronegativity and hydrophobicity. The hexameric nature of arthropod tyrosinases suggests that these proteins were the ideal predecessors from which to develop the oxygen-carrier protein haemocyanin, with its allosteric and co-operative properties, later on.
authors.affiliation: Institut für Molekulare Biophysik, Johannes Gutenberg Universität Mainz, Jakob Welder Weg 26, D-55128 Mainz, Germany.
authors.forename: Elmar
authors.initials: E
authors.lastname: Jaenicke
authors.forename: Heinz
authors.initials: H
authors.lastname: Decker
mesh_terms: D000818:Animals; D003400:Astacoidea / Q000201:enzymology; D002852:Chromatography, Ion Exchange; D003445:Crustacea / Q000201:enzymology*; D019143:Evolution, Molecular; D006458:Hemolymph / Q000201:enzymology; D007700:Kinetics; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D014442:Monophenol Monooxygenase / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D013045:Species Specificity
chemical_list: D046911:Macromolecular Substances; D014442:Monophenol Monooxygenase