TY - JOUR

T1 - Novel polyphenol oxidase mined from a metagenome expression library of bovine rumen

T2 - biochemical properties, structural analysis, and phylogenetic relationships

AU - Beloqui, Ana

AU - Pita, Marcos

AU - Polaina, Julio

AU - Martínez-Arias, Arturo

AU - Golyshina, Olga V

AU - Zumárraga, Miren

AU - Yakimov, Michail M

AU - García-Arellano, Humberto

AU - Alcalde, Miguel

AU - Fernández, Víctor M

AU - Elborough, Kieran

AU - Andreu, José M

AU - Ballesteros, Antonio

AU - Plou, Francisco J

AU - Timmis, Kenneth N

AU - Ferrer, Manuel

AU - Golyshin, Peter N

PY - 2006/8/11

Y1 - 2006/8/11

N2 - RL5, a gene coding for a novel polyphenol oxidase, was identified through activity screening of a metagenome expression library from bovine rumen microflora. Characterization of the recombinant protein produced in Escherichia coli revealed a multipotent capacity to oxidize a wide range of substrates (syringaldazine > 2,6-dimethoxyphenol > veratryl alcohol > guaiacol > tetramethylbenzidine > 4-methoxybenzyl alcohol > 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) > phenol red) over an unusually broad range of pH from 3.5 to 9.0. Apparent Km and kcat values for ABTS, syringaldazine, and 2,6-dimetoxyphenol obtained from steady-state kinetic measurements performed at 40 degrees C, pH 4.5, yielded values of 26, 0.43, and 0.45 microm and 18, 660, and 1175 s(-1), respectively. The Km values for syringaldazine and 2,6-dimetoxyphenol are up to 5 times lower, and the kcat values up to 40 times higher, than values previously reported for this class of enzyme. RL5 is a 4-copper oxidase with oxidation potential values of 745, 400, and 500 mV versus normal hydrogen electrode for the T1, T2, and T3 copper sites. A three-dimensional model of RL5 and site-directed mutants were generated to identify the copper ligands. Bioinformatic analysis of the gene sequence and the sequences and contexts of neighboring genes suggested a tentative phylogenetic assignment to the genus Bacteroides. Kinetic, electrochemical, and EPR analyses provide unequivocal evidence that the hypothetical proteins from Bacteroides thetaiotaomicron and from E. coli, which are closely related to the deduced protein encoded by the RL5 gene, are also multicopper proteins with polyphenol oxidase activity. The present study shows that these three newly characterized enzymes form a new family of functional multicopper oxidases with laccase activity related to conserved hypothetical proteins harboring the domain of unknown function DUF152 and suggests that some other of these proteins may also be laccases.

AB - RL5, a gene coding for a novel polyphenol oxidase, was identified through activity screening of a metagenome expression library from bovine rumen microflora. Characterization of the recombinant protein produced in Escherichia coli revealed a multipotent capacity to oxidize a wide range of substrates (syringaldazine > 2,6-dimethoxyphenol > veratryl alcohol > guaiacol > tetramethylbenzidine > 4-methoxybenzyl alcohol > 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) > phenol red) over an unusually broad range of pH from 3.5 to 9.0. Apparent Km and kcat values for ABTS, syringaldazine, and 2,6-dimetoxyphenol obtained from steady-state kinetic measurements performed at 40 degrees C, pH 4.5, yielded values of 26, 0.43, and 0.45 microm and 18, 660, and 1175 s(-1), respectively. The Km values for syringaldazine and 2,6-dimetoxyphenol are up to 5 times lower, and the kcat values up to 40 times higher, than values previously reported for this class of enzyme. RL5 is a 4-copper oxidase with oxidation potential values of 745, 400, and 500 mV versus normal hydrogen electrode for the T1, T2, and T3 copper sites. A three-dimensional model of RL5 and site-directed mutants were generated to identify the copper ligands. Bioinformatic analysis of the gene sequence and the sequences and contexts of neighboring genes suggested a tentative phylogenetic assignment to the genus Bacteroides. Kinetic, electrochemical, and EPR analyses provide unequivocal evidence that the hypothetical proteins from Bacteroides thetaiotaomicron and from E. coli, which are closely related to the deduced protein encoded by the RL5 gene, are also multicopper proteins with polyphenol oxidase activity. The present study shows that these three newly characterized enzymes form a new family of functional multicopper oxidases with laccase activity related to conserved hypothetical proteins harboring the domain of unknown function DUF152 and suggests that some other of these proteins may also be laccases.

KW - Amino Acid Sequence

KW - Animals

KW - Bacteroides/enzymology

KW - Catechol Oxidase/chemistry

KW - Cattle

KW - Escherichia coli/metabolism

KW - Gene Library

KW - Intestines/microbiology

KW - Kinetics

KW - Molecular Sequence Data

KW - Mutation

KW - Oxidation-Reduction

KW - Phylogeny

KW - Sequence Homology, Amino Acid

U2 - 10.1074/jbc.M600577200

DO - 10.1074/jbc.M600577200

M3 - Article

C2 - 16740638

VL - 281

SP - 22933

EP - 22942

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

SN - 0021-9258

IS - 32

ER -