Enzymatic Synthesis of New Oligosaccharides Using Mannosyltransferases from Candida Species and Their NMR Assignments

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The outer layer of the cell wall of pathogenic fungi, Candida species, consists of mannan, which plays an important role in infection. In this study, we synthesized several oligosaccharides using mannosyltransferases obtained from Candida parapsilosis and Candida albicans. Namely, we synthesized mannotetraoses [Manα1→ 2Manα1→3Manα1→2Man and Manα1→3(Manα1→6)Manα1→2Man] from mannotriose, Manα1→3Manα1→ 2Man, and mannohexaoses [Manα1→2Manα1→3Manα1→3Manα1→2Manα1→2Man and Manα1→3(Manα1→6)Manα1→3Manα1→2Manα1→2Man] from mannopentaose, Manα1→3Manα1→3Manα1→2Manα1→2Man. The linkage sequence of these oligosaccharides was identified by a sequential 1H-NMR assignment method combined with rotating frame nuclear Overhauser enhancement spectroscopy and relayed coherence transfer spectroscopy. The steric effect by the α-1,6-linked branching mannose residue to the H-1 proton chemical shift of the neighboring 3-O-substituted mannose residue was different from that of the 2-O-substituted mannose residue. These oligosaccharides having novel structures seem to be useful as the substrate or ligand for glycomics.