title: Enzymatic Synthesis of Galactosylated Serine/Threonine Derivatives by β-Galactosidase from Escherichia coli.
abstract: The transgalactosylations of serine/threonine derivatives were investigated using β-galactosidase from Escherichia coli as biocatalyst. Using ortho-nitrophenyl-β-D-galactoside as donor, the highest bioconversion yield of transgalactosylated N-carboxy benzyl L-serine benzyl ester (23.2%) was achieved in heptane:buffer medium (70:30), whereas with the lactose, the highest bioconversion yield (3.94%) was obtained in the buffer reaction system. The structures of most abundant galactosylated serine products were characterized by MS/MS. The molecular docking simulation revealed that the binding of serine/threonine derivatives to the enzyme's active site was stronger (-4.6~-7.9 kcal/mol) than that of the natural acceptor, glucose, and mainly occurred through interactions with aromatic residues. For N-tert-butoxycarbonyl serine methyl ester (6.8%) and N-carboxybenzyl serine benzyl ester (3.4%), their binding affinities and the distances between their hydroxyl side chain and the 1'-OH group of galactose moiety were in good accordance with the quantified bioconversion yields. Despite its lower predicted bioconversion yield, the high experimental bioconversion yield obtained with N-carboxybenzyl serine methyl ester (23.2%) demonstrated the importance of the thermodynamically-driven nature of the transgalactosylation reaction.
authors.affiliation: Department of Food Science and Agricultural Chemistry, McGill University, 21,111 Lakeshore, Ste Anne de Bellevue, QC H9X-3V9, Canada. sooyoun.seo@mail.mcgill.ca.
authors.forename: Sooyoun
authors.initials: S
authors.lastname: Seo
authors.affiliation: INSERM UMR_S 1134, Dynamique des Structures et Interactions des Macromolécules Biologiques (DSIMB), University Paris Diderot, Sorbonne Paris Cité, INTS, Laboratory of excellence, GR-Ex, 6, rue Alexandre Cabanel, 75739 Paris Cedex 15, France. joseph.rebehmed@univ-paris-diderot.fr.
authors.forename: Joseph
authors.initials: J
authors.lastname: Rebehmed
authors.affiliation: INSERM UMR_S 1134, Dynamique des Structures et Interactions des Macromolécules Biologiques (DSIMB), University Paris Diderot, Sorbonne Paris Cité, INTS, Laboratory of excellence, GR-Ex, 6, rue Alexandre Cabanel, 75739 Paris Cedex 15, France. alexandre.debrevern@univ-paris-diderot.fr.
authors.forename: Alexandre G
authors.initials: AG
authors.lastname: de Brevern
authors.affiliation: Department of Food Science and Agricultural Chemistry, McGill University, 21,111 Lakeshore, Ste Anne de Bellevue, QC H9X-3V9, Canada. salwa.karboune@mcgill.ca.
authors.forename: Salwa
authors.initials: S
authors.lastname: Karboune
mesh_terms: D055162:Biocatalysis; D029968:Escherichia coli Proteins / Q000737:chemistry*; D005690:Galactose / Q000737:chemistry*; D062105:Molecular Docking Simulation; D012694:Serine / Q000031:analogs & derivatives* / Q000737:chemistry; D013912:Threonine / Q000031:analogs & derivatives* / Q000737:chemistry; D001616:beta-Galactosidase / Q000737:chemistry*
chemical_list: D029968:Escherichia coli Proteins; D013912:Threonine; D012694:Serine; D001616:beta-Galactosidase; D005690:Galactose
keywords: binding affinities; galactosyl acceptor; molecular docking; serine/threonine derivatives; transgalactosylation; β-galactosidase