title: Rational design of Bacillus stearothermophilus US100 L-arabinose isomerase: potential applications for D-tagatose production.
abstract: L-arabinose isomerases catalyze the bioconversion of D-galactose into D-tagatose. With the aim of producing an enzyme optimized for D-tagatose production, three Bacillus stearothermophilus US100 L-arabinose isomerase mutants were constructed, purified and characterized. Our results indicate that mutant Q268K was significantly more acidotolerant and more stable at acidic pH than the wild-type enzyme. The N175H mutant has a broad optimal temperature range from 50 to 65 degrees C. With the aim of constructing an acidotolerant mutant working at relatively low temperatures we generated the Q268K/N175H construct. This double mutant displays an optimal pH in the range 6.0-7.0 and an optimal activity around 50-65 degrees C, temperatures at which the enzyme was stable without addition of metal ions.
authors.affiliation: Laboratoire d'Enzymes et de Métabolites des Procaryotes, Centre de Biotechnologie de Sfax, Sfax-Tunisie, Tunisia.
authors.forename: Moez
authors.initials: M
authors.lastname: Rhimi
authors.forename: Nushin
authors.initials: N
authors.lastname: Aghajari
authors.forename: Michel
authors.initials: M
authors.lastname: Juy
authors.forename: Hichem
authors.initials: H
authors.lastname: Chouayekh
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Maguin
authors.forename: Richard
authors.initials: R
authors.lastname: Haser
authors.forename: Samir
authors.initials: S
authors.lastname: Bejar
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001411:Geobacillus stearothermophilus / Q000201:enzymology* / Q000235:genetics; D006601:Hexoses / Q000096:biosynthesis*; D006863:Hydrogen-Ion Concentration; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D016133:Polymerase Chain Reaction; D013696:Temperature
chemical_list: D006601:Hexoses; D019747:Aldose-Ketose Isomerases; C019715:L-arabinose isomerase; C030192:tagatose