title: The Structure of a Plant Tyrosinase from Walnut Leaves Reveals the Importance of "Substrate-Guiding Residues" for Enzymatic Specificity.
abstract: Tyrosinases and catechol oxidases are members of the class of type III copper enzymes. While tyrosinases accept both mono- and o-diphenols as substrates, only the latter substrate is converted by catechol oxidases. Researchers have been working for decades to elucidate the monophenolase/diphenolase specificity on a structural level and have introduced an early hypothesis that states that the reason for the lack of monophenolase activity in catechol oxidases may be its structurally restricted active site. However, recent structural and biochemical studies of this enzyme class have raised doubts about this theory. Herein, the first crystal structure of a plant tyrosinase (from Juglans regia) is presented. The structure reveals that the distinction between mono- and diphenolase activity does not depend on the degree of restriction of the active site, and thus a more important role for amino acid residues located at the entrance to and in the second shell of the active site is proposed.
authors.affiliation: Institut für Biophysikalische Chemie, Fakultät für Chemie, Universität Wien, Althanstraße 14, 1090 Wien (Austria) http://www.bpc.univie.ac.at.
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Bijelic
authors.affiliation: Institut für Biophysikalische Chemie, Fakultät für Chemie, Universität Wien, Althanstraße 14, 1090 Wien (Austria) http://www.bpc.univie.ac.at.
authors.forename: Matthias
authors.initials: M
authors.lastname: Pretzler
authors.affiliation: Institut für Biophysikalische Chemie, Fakultät für Chemie, Universität Wien, Althanstraße 14, 1090 Wien (Austria) http://www.bpc.univie.ac.at.
authors.forename: Christian
authors.initials: C
authors.lastname: Molitor
authors.affiliation: Institut für Biophysikalische Chemie, Fakultät für Chemie, Universität Wien, Althanstraße 14, 1090 Wien (Austria) http://www.bpc.univie.ac.at.
authors.forename: Florime
authors.initials: F
authors.lastname: Zekiri
authors.affiliation: Institut für Biophysikalische Chemie, Fakultät für Chemie, Universität Wien, Althanstraße 14, 1090 Wien (Austria) http://www.bpc.univie.ac.at. annette.rompel@univie.ac.at.
authors.forename: Annette
authors.initials: A
authors.lastname: Rompel
mesh_terms: D031324:Juglans / Q000201:enzymology*; D008958:Models, Molecular; D014442:Monophenol Monooxygenase / Q000737:chemistry* / Q000378:metabolism*; D018515:Plant Leaves / Q000201:enzymology*; D011487:Protein Conformation; D013379:Substrate Specificity
chemical_list: D014442:Monophenol Monooxygenase
keywords: enzyme catalysis; metalloenzymes; oxidoreductases; structure elucidation; tyrosinase