title: Oxidation of Monolignols by Members of the Berberine Bridge Enzyme Family Suggests a Role in Plant Cell Wall Metabolism.
abstract: Plant genomes contain a large number of genes encoding for berberine bridge enzyme (BBE)-like enzymes. Despite the widespread occurrence and abundance of this protein family in the plant kingdom, the biochemical function remains largely unexplored. In this study, we have expressed two members of the BBE-like enzyme family from Arabidopsis thaliana in the host organism Komagataella pastoris. The two proteins, termed AtBBE-like 13 and AtBBE-like 15, were purified, and their catalytic properties were determined. In addition, AtBBE-like 15 was crystallized and structurally characterized by x-ray crystallography. Here, we show that the enzymes catalyze the oxidation of aromatic allylic alcohols, such as coumaryl, sinapyl, and coniferyl alcohol, to the corresponding aldehydes and that AtBBE-like 15 adopts the same fold as vanillyl alcohol oxidase as reported previously for berberine bridge enzyme and other FAD-dependent oxidoreductases. Further analysis of the substrate range identified coniferin, the glycosylated storage form of coniferyl alcohol, as a substrate of the enzymes, whereas other glycosylated monolignols were rather poor substrates. A detailed analysis of the motifs present in the active sites of the BBE-like enzymes in A. thaliana suggested that 14 out of 28 members of the family might catalyze similar reactions. Based on these findings, we propose a novel role of BBE-like enzymes in monolignol metabolism that was previously not recognized for this enzyme family.
authors.affiliation: From the Institutes of Biochemistry.
authors.forename: Bastian
authors.initials: B
authors.lastname: Daniel
authors.affiliation: the Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria, the ACIB GmbH, 8010 Graz, Austria, and.
authors.forename: Tea
authors.initials: T
authors.lastname: Pavkov-Keller
authors.affiliation: From the Institutes of Biochemistry.
authors.forename: Barbara
authors.initials: B
authors.lastname: Steiner
authors.affiliation: the Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria, the ACIB GmbH, 8010 Graz, Austria, and.
authors.forename: Andela
authors.initials: A
authors.lastname: Dordic
authors.affiliation: Biotechnology and Biochemical Engineering, and.
authors.forename: Alexander
authors.initials: A
authors.lastname: Gutmann
authors.affiliation: Biotechnology and Biochemical Engineering, and.
authors.forename: Bernd
authors.initials: B
authors.lastname: Nidetzky
authors.affiliation: Molecular Biotechnology, Graz University of Technology, 8010 Graz, Austria.
authors.forename: Christoph W
authors.initials: CW
authors.lastname: Sensen
authors.affiliation: the Section for Crop Sciences, Copenhagen University, 2630 Copenhagen, Denmark.
authors.forename: Eric
authors.initials: E
authors.lastname: van der Graaff
authors.affiliation: From the Institutes of Biochemistry.
authors.forename: Silvia
authors.initials: S
authors.lastname: Wallner
authors.affiliation: the Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria.
authors.forename: Karl
authors.initials: K
authors.lastname: Gruber
authors.affiliation: From the Institutes of Biochemistry, peter.macheroux@tugraz.at.
authors.forename: Peter
authors.initials: P
authors.lastname: Macheroux
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics; D002384:Catalysis; D020134:Catalytic Domain; D002473:Cell Wall / Q000201:enzymology*; D018360:Crystallography, X-Ray; D007700:Kinetics; D008031:Lignin / Q000378:metabolism*; D010084:Oxidation-Reduction; D010089:Oxidoreductases, N-Demethylating / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity
chemical_list: D029681:Arabidopsis Proteins; D008031:Lignin; C071690:reticuline oxidase; C000602106:BBE-like 13 protein, Arabidopsis; C000602105:BBE-like 15 protein, Arabidopsis; D010089:Oxidoreductases, N-Demethylating
keywords: Arabidopsis thaliana; enzyme catalysis; flavin adenine dinucleotide (FAD); flavoprotein; plant biochemistry