FWF - BBE - The family of berberine bridge enzymes in plants

Berberine bridge enzyme (BBE)-like enzymes are central catalysts in the biosynthesis of plant alkaloids and terpenes. In the proposed study we will characterize 28 genes encoding BBE-like enzymes in the model plant A. thaliana. Recently, we have been able to demonstrate that a member of the BBE-like enzyme family from A. thaliana (termed AtBBE15) catalyses the oxidation of monolignols, such as p-coumaryl alcohol, to their corresponding aldehydes indicating a role of this enzyme in plant cell wall metabolism. Since 14 other members of the BBE-like enzyme family share the same active site composition we suspect that they have similar catalytic properties. Thus one aim of our study will be to demonstrate that these BBE-like enzymes are equally involved in the oxidation of plant monolignols. On the other hand, our analysis has shown that several other groups of BBE-like enzymes are present in A. thaliana that have distinct active sites and thus it is likely that these enzymes play different roles. Therefore the second major aim of our study is to identify the biochemical reactions catalysed by these enzymes and to define their substrate specificity in order to understand their function in planta. Additionally, we will select representatives from each distinct group in the BBE-like family to elucidate the three-dimensional structure of the proteins by means of X-ray crystallography. This effort will be complemented by metabolite analysis of loss- and gain-of-function lines to facilitate identification of potential substrates for the individual BBE-like enzymes. Through this integrative approach of structural biology, biochemistry and plant physiology we expect to define the role of BBE-like enzymes in A. thaliana.