Insights into sucrose isomerization from crystal structures of the Pseudomonas mesoacidophila MX-45 sucrose isomerase, MutB
Résumé
Three-dimensional structures of a sucrose isomerase from Pseudomonas mesoacidophila MX-45, forming mainly trehalulose have been solved to resolutions in the range 1.8-2.2 angstrom . Native and mutant complexes give, for the first time, a thorough insight into substrate binding and recognition, and product specificities of these enzymes. This study has pinpointed essential residues for binding the substrate sucrose, and hereby given detailed information on the interactions between the enzyme active site and glucosyl- and fructosyl moieties. Moreover, the 3-D structures revealed an aromatic clamp formed by two phenylalanines, which plays an essential role in recognition of the substrate and in controlling the reaction specificity.Three-dimensional structures of a sucrose isomerase from Pseudomonas mesoacidophila MX-45, forming mainly trehalulose have been solved to resolutions in the range 1.8-2.2 angstrom . Native and mutant complexes give, for the first time, a thorough insight into substrate binding and recognition, and product specificities of these enzymes. This study has pinpointed essential residues for binding the substrate sucrose, and hereby given detailed information on the interactions between the enzyme active site and glucosyl- and fructosyl moieties. Moreover, the 3-D structures revealed an aromatic clamp formed by two phenylalanines, which plays an essential role in recognition of the substrate and in controlling the reaction specificity.