The carbohydrate binding pocket of IPO was confirmed at loops b13 and b14 by the structures of IPO-Me-Glc, IPO-Me-Man and IPO-Me-Gal (as shown in Figure 2B with green mesh). In the chain A of IPO-Me-Glc, 9 hydrogen bonds are formed by the residues Gly21, Tyr97, Gly141, Trp142, Tyr143 and Asp145 of IPO and the atoms O1, O3, O4, O5, and O6 of Me-Glc ( Figure 3A and Table 1 ). The atom C7 of Me-Glc is involved in the methyl carbon (Me)…p interaction with Trp142 of IPO. The hydrogen bonds are slightly different between chain A and chains B to D. The hydrogen bonds of chains B to D are formed between the same residues of chain A and Me-Man, except for Table 1 ). The differences might result from the binding of cadmium ion (Cd 2+ ). In chains B to D, the Cd 2+ atom forms 5 coordinates by the O atom of the carbonyl group of Asn19, OG atom of Ser18, and 3 water molecules. One of the 3 water molecules forms a hydrogen bond with Asp145 ( Figure 3B ).