EC 4.2.2.16     
Accepted name: levan fructotransferase (DFA-IV-forming)
Reaction: Produces di-β-D-fructofuranose 2,6′:2′,6-dianhydride (DFA IV) by successively eliminating the diminishing (2→6)-β-D-fructan (levan) chain from the terminal D-fructosyl-D-fructosyl disaccharide
Other name(s): 2,6-β-D-fructan D-fructosyl-D-fructosyltransferase (forming di-β-D-fructofuranose 2,6′:2′,6-dianhydride); levan fructotransferase; 2,6-β-D-fructan lyase (di-β-D-fructofuranose-2,6′:2′,6-dianhydride-forming)
Systematic name: (2→6)-β-D-fructan lyase (di-β-D-fructofuranose-2,6′:2′,6-dianhydride-forming)
Comments: This enzyme, like EC 4.2.2.17 [inulin fructotransferase (DFA-I-forming)] and EC 4.2.2.18 [inulin fructotransferase (DFA-III-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.  Song, K.B., Bae, K.S., Lee, Y.B., Lee, K.Y. and Rhee, S.K. Characteristics of levan fructotransferase from Arthrobacter ureafaciens K2032 and difructose anhydride IV formation from levan. Enzyme Microb. Technol. 27 (2000) 212–218. [PMID: 10899545]
2.  Jang, K.H., Ryu, E.J., Park, B.S., Song, K.B., Kang, S.A., Kim, C.H., Uhm, T.B., Park, Y.I. and Rhee, S.K. Levan fructotransferase from Arthrobacter oxydans, J 17-21 catalyzes the formation of the di-D-fructose dianhydride IV from levan. J. Agric. Food Chem. 51 (2003) 2632–2636. [PMID: 12696949]
3.  Saito, K. and Tomita, F. Difructose anhydrides: Their mass-production and physiological functions. Biosci. Biotechnol. Biochem. 64 (2000) 1321–1327. [PMID: 10945246]
[EC 4.2.2.16 created 2004]