title: The process for the activation of frog epidermis pro-tyrosinase.
abstract: 1. Purified pro-tyrosinase from epidermis of the frog Rana esculenta ridibunda can be activated in vitro by several proteinases (trypsin, alpha-chymotrypsin, Pronase) and by light. 2. Both pro-tyrosinase and tyrosinase are composed of a single type of subunit having pI 7.2 and approximate molecular weights 68000 and 62000 respectively. A peptide of low molecular weight is released as a consequence of the proteolytic activation. Pro-tyrosinase and tyrosinase have different quaternary structures, the proenzyme being a dimer of Mr approx. 115000 and the enzyme a tetramer of Mr approx. 210 000. 3. The activation process was affected by several agents (L-3,4-dihydroxyphenylalanine, urea, formamide) that prevented, partially or totally, the activation of pro-tyrosinase. 4. The activation of pro-tyrosinase seems to be the result of a cleavage of the polypeptide chain that determines changes in tertiary or quaternary structure.
mesh_terms: D000818:Animals; D004156:Catechol Oxidase / Q000378:metabolism*; D010450:Endopeptidases / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004792:Enzyme Precursors / Q000302:isolation & purification / Q000378:metabolism*; D004817:Epidermis / Q000201:enzymology; D007700:Kinetics; D008027:Light; D008954:Models, Biological; D014442:Monophenol Monooxygenase / Q000302:isolation & purification / Q000378:metabolism*; D011895:Rana ridibunda
chemical_list: D004792:Enzyme Precursors; D004156:Catechol Oxidase; D014442:Monophenol Monooxygenase; D010450:Endopeptidases