Produces alpha-D-fructofuranose beta-D-fructofuranose 1,2':2,3'-dianhydride (DFA III) by successively eliminating the diminishing (2->1)-beta-D-fructan (inulin) chain from the terminal D-fructosyl-D-fructosyl disaccharide.
Comment
This enzyme, like EC 4.2.2.16 [levan fructotransferase (DFA-IV-forming)] and EC 4.2.2.17 [inulin fructotransferase (DFA-I-forming)], sequentially eliminates disaccharides from the non-reducing terminus of the fructan chain, with the disaccharide leaving as a difructose dianhydride. These enzymes have long been known as fructotransferases, so this is retained in the accepted name. Since the transfer is intramolecular, the reaction is an elimination and, hence, the enzyme is a lyase, belonging in EC 4.
History
EC 4.2.2.18 created 1976 as EC 2.4.1.93, transferred 2004 to EC 4.2.2.18, modified 2025
