Structural studies of the sucrose isomerase MutB fromPseudomonas mesoacidophila

Abstract

The sucrose isomerase, MutB, from Pseudomonas mesoacidophila belongs to glycoside hydrolase family 13, and catalyzes the isomerization of sucrose into isomaltulose and trehalulose [1]. The 64 kDa enzyme has been crystallized [2] and the three dimensional structure of MutB has been solved to 1.6 A resolution by the molecular replacement method using the isomaltulose synthase, PalI, from Klebsiella sp. LX3 as a search model [3]. The overall structure of MutB is made up of three domains: an N-terminal and catalytic (β/α)8 domain, a subdomain and a C-terminal domain made up of seven β-strands [4]. The structures of various complexes with inhibitors and/or substrate analogues have been obtained and are currently under refinement. Once the detailed analyses of these structures have been completed, a better understanding of the molecular basis of sucrose decomposition, isomerization as well as the selectivity of this enzyme leading to the formation of different products should be gained.