Structural highlights
Publication Abstract from PubMedXanthophyllomyces dendrorhous beta-fructofuranosidase (XdINV) is a highly glycosylated dimeric enzyme that hydrolyzes sucrose and releases fructose from various fructooligosaccharides (FOS) and fructans. It also catalyzes the synthesis of FOS, prebiotics that stimulate the growth of beneficial bacteria in human gut. In contrast to most fructosylating enzymes, XdINV produces neo-FOS, which makes it an interesting biotechnology target. We present here its three-dimensional structure, which shows the expected bimodular arrangement but, also, a long extension of its C-terminus that together with a N-linked glycan mediate the formation of an unusual dimer. This dimer shapes two active sites communicated by a long channel, which might indicate its potential ability to house branched fructans. This arrangement could be representative of a group of GH32 yeast enzymes having the traits observed in XdINV. Inactivated D80A mutant was used to obtain complexes with relevant substrates and products, their crystals structures showing at least four binding subsites at each active site. Moreover, two different positions are observed from subsite +2 depending of the substrate and, thus, a flexible loop (Glu334-His343) is essential in binding sucrose and beta(2-1) linked oligosaccharides. Conversely, beta(2-6) and neo-type substrates are accommodated mainly by stacking to Trp105, explaining the production of neokestose and the efficient fructosylating activity of XdINV on alpha-glucosides. The role of relevant residues has been investigated by mutagenesis and kinetics measurements and a model for the transfructosylating reaction has been proposed. The plasticity of its active site makes XdINV a valuable and flexible biocatalyst to produce novel bioconjugates. Structural analysis of beta-fructofuranosidase from Xanthophyllomyces dendrorhous reveals unique features and the crucial role of N-glycosylation in oligomerization and activity.,Ramirez-Escudero M, Gimeno-Perez M, Gonzalez B, Linde D, Merdzo Z, Fernandez-Lobato M, Sanz-Aparicio J J Biol Chem. 2016 Jan 28. pii: jbc.M115.708495. PMID:26823463[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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