FIGURE 1.

General reaction catalyzed by GH-J clan enzymes through a double displacement mechanism that involves a covalent intermediate. The β-(2→1)-linked fructan represented (the donor substrate) would be hydrolyzed in the second step of the reaction when water is the acceptor substrate of the fructosyl (r = H). In the case of an oligosaccharide acting as acceptor, a transfructosylating product is obtained. The inulin-type scaffold is: sucrose (n = 0), 1-kestose (n = 1), nystose (n = 2), fructosylnystose (n = 3), inulin (n ≈ 30–50).