EC 4.2.2.18     
Accepted name: inulin fructotransferase (DFA-III-forming)
Reaction: Produces α-D-fructofuranose β-D-fructofuranose 1,2′:2,3′-dianhydride (DFA III) by successively eliminating the diminishing (2→1)-β-D-fructan (inulin) chain from the terminal D-fructosyl-D-fructosyl disaccharide.
Other name(s): inulin fructotransferase (DFA-III-producing); inulin fructotransferase (depolymerizing); inulase II; inulinase II; inulin fructotransferase (depolymerizing, difructofuranose-1,2′:2,3′-dianhydride-forming); inulin D-fructosyl-D-fructosyltransferase (1,2′:2,3′-dianhydride-forming); inulin D-fructosyl-D-fructosyltransferase (forming α-D-fructofuranose β-D-fructofuranose 1,2′:2,3′-dianhydride); 2,1-β-D-fructan lyase (α-D-fructofuranose-β-D-fructofuranose-1,2′:2,3′-dianhydride-forming)
Systematic name: (2→1)-β-D-fructan lyase (α-D-fructofuranose-β-D-fructofuranose-1,2′:2,3′-dianhydride-forming)
Comments: This enzyme, like EC 4.2.2.16 [levan fructotransferase (DFA-IV-forming)] and EC 4.2.2.17 [inulin fructotransferase (DFA-I-forming)] eliminates the fructan chain from the terminal disaccharide leaving 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.
References:
1.  Uchiyama, T. Action of Arthrobacter ureafaciens inulinase II on several oligofructans and bacterial levans. Biochim. Biophys. Acta 397 (1975) 153–163. [PMID: 1148257]
2.  Uchiyama, T., Niwa, S. and Tanaka, K. Purification and properties of Arthrobacter ureafaciens inulase II. Biochim. Biophys. Acta 315 (1973) 412–420.
[EC 4.2.2.18 created 1976 as EC 2.4.1.93, transferred 2004 to EC 4.2.2.18]