Berberine bridge enzyme-like proteins: From characterization to application

Description

Flavoproteins are a diverse protein class employing an isoalloxazine ring for catalysis in form of the flavin mononucleotide (FMN) or the flavin adenine dinucleotide (FAD). Among them, is the berberine bridge enzyme-like (BBE-like) protein family (pfam 08031) that was named after the berberine bridge enzyme (EcBBE) from California poppy (Eschscholzia californica). BBE-like proteins form a multigene family in plants and the number of members varies from one in the moss Physcomitrella patens to 28 in Arabidopsis thaliana and 57 in the Western Balsam Poplar (Populus trichocarpa). Despite of the frequent occurrence of these proteins their function is largely unknown. Therefore, we chose to investigate the BBE-like proteins occurring in A. thaliana to broaden our understanding of this protein family. Presented will be the structural and biochemical characterization of AtBBE-like protein 15 and 28, the application of an engineered AtBBE-like 15 variant as biocatalyst, the role of AtBBE-like 15 in plant physiology and the development of the BBE-like protein family in the plant kingdom.
Our analysis of the AtBBE-like protein family reveals that there are four frequently occurring active site types1,2. AtBBE-like protein 15 is a representative of the most abundant type, therefore the enzyme can serve as a paradigm for the majority of BBE-like proteins1. The enzyme was identified as monolignol dehydrogenase, an activity that was not recognized for this protein family before. Additionally, the enzyme was rationally engineered towards higher oxygen reactivity and the potential of the enzyme as biocatalyst for oxidative reactions was tested3. Experiments with AtBBE-like 15 knock out plants revealed a perturbation in the lignin content and total amount lignin of these plants. This indicates that monolignol dehydrogenases are responsible for the manipulation of the monolignol pool and represent an electron delivery system to fuel the lignification that was previously not recognized.

References
1 Daniel, B. et al. (2015), Oxidation of monolignols by members of the berberine bridge enzyme family suggests a role in cell wall metabolism. J. Biol. Chem. 290: 18770–18781.
2 Daniel, B. et al. (2016), Structure of a berberine bridge enzyme-like enzyme with an active site specific to the plant family of Brassicaceae. PLoS ONE 11, 6: S. e0156892.
3 Pils, S. et al. (2016) Characterization of a monolignol oxidoreductase from Arabidopsis thaliana for biocatalytic applications. J. Mol. Catal. B: Enzym. in press.

Period	5 Jul 2017
Event title	19th International Symposium on Flavins and Flavoproteins
Event type	Conference
Location	Groningen, NetherlandsShow on map
Degree of Recognition	International