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Magali Remaud Simeon

Magali Remaud Simeon

INSA - Université de Toulouse, France

Title: Mixing enzyme discovery with engineering for sucrose-derived bioproducts: The case of GH13 and GH70 polymerases

Biography

Biography: Magali Remaud Simeon

Abstract

The exploration of the natural diversity, through data mining, functional genomics and/or metagenomics is an effi cient mean
to discover enzymes showing new functions or improved performances. Th ese approaches can be further completed or run
in parallel with semi-rational protein engineering based on structure/function studies or directed molecular evolution inspired
from nature. Which of these alternatives are the best ones, in terms of eff ort, rapidity and effi ciency? Th is is an open question
to which a defi nite answer can be hardly formulated a priori. For illustration, we will take a few examples from our most recent
work on glucansucrases from GH13 and GH70 families. Th ese enzymes are naturally very effi cient transglucosylases. Th ey
use sucrose as substrate and catalyze polymerization of its glucosyl units as a main reaction. Depending on their specifi city,
structures varying in size as well as in glycosidic linkage types can be obtained, thus giving access to an interesting panel of
biopolymers. A campaign of genome sequencing and data mining allowed the isolation of atypical enzymes with new product
specifi cities. In particular, a hyper effi cient polymerase producing a gel-like polymer and, in contrast an enzyme synthesizing
directly from sucrose a polymer of well-controlled low molar mass could be characterized. Structure-function studies combined
with mutagenesis assays allowed us to decipher some of the molecular mechanisms behind the control of the polymer size and
enzyme processivity. Another key property of these catalysts is coming from their ability to glucosylate a broad spectrum of
hydroxylated molecules. Computational protein design, structurally-guided engineering and also random approaches such as
neutral evolution was implemented for a fi ne tuning of their acceptor specifi city toward non-natural acceptors such chemically
protected disaccharides for vaccinal applications, polyol, fl avonoids, or various chemicals. Th ese various approaches will be
described and discussed with regard to the engineering objectives.