Identification by saturation mutagenesis of a single residue involved in the alpha-galactosidase AgaB regioselectivity.
The alpha-galactosidase AgaB of Bacillus stearothermophilus displays a major 1,6 and a minor 1,3 regioselectivity. The wild-type enzyme was subjected to directed evolution (random mutagenesis and in vitro recombination) using a double screening strategy based on the elimination of the 1,6 regioselectivity and the analysis by TLC of the transglycosylation products. One of the AgaB mutants (E500) exhibited a new 1,2 regioselectivity and a rather high level of transglycosylation. The corresponding gene contains 10 mutations compared to the agaB gene and we demonstrated by saturation mutagenesis that the G442R substitution strongly contributes to the emergence of this new regioselectivity. Moreover, other single point mutations at this position led to new mutants displaying other kinds of regioselectivity demonstrating the importance of this position in the subtle kinetic control of transglycosylation.
Dion
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M
Unité de Recherches sur la Biocatalyse, FRE-CNRS no. 2230 Faculté des Sciences et des Techniques, 2 rue de la Houssinière, BP 92208, F-44322 Nantes Cedex 03, France. Michel.Dion@chimbio.univ-nantes.fr
Osanjo
G
G
André
C
C
Spangenberg
P
P
Rabiller
C
C
Tellier
C
C
D003001:Cloning, Molecular; D003062:Codon / Q000235:genetics; D019020:Directed Molecular Evolution; D004187:Disaccharides / Q000096:biosynthesis; D001411:Geobacillus stearothermophilus / Q000201:enzymology* / Q000235:genetics*; D006031:Glycosylation; D006596:Hexosaminidases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D016296:Mutagenesis / Q000235:genetics*; D019906:Nuclear Magnetic Resonance, Biomolecular; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D048809:alpha-N-Acetylgalactosaminidase
D003062:Codon; D004187:Disaccharides; D006596:Hexosaminidases; D048809:alpha-N-Acetylgalactosaminidase