ID   4.2.2.16
DE   levan fructotransferase (DFA-IV-forming).
AN   2,6-beta-D-fructan D-fructosyl-D-fructosyltransferase (forming di-beta-D-
AN   fructofuranose 2,6':2',6-dianhydride).
AN   levan fructotransferase.
CA   Produces di-beta-D-fructofuranose 2,6':2',6-dianhydride (DFA IV) by
CA   successively eliminating the diminishing (2->6)-beta-D-fructan (levan)
CA   chain from the terminal D-fructosyl-D-fructosyl disaccharide.
CC   -!- This enzyme, like EC 4.2.2.17 and EC 4.2.2.18 eliminates the fructan
CC       chain from the terminal disaccharide leaving a difructose
CC       dianhydride.
CC   -!- These enzymes have long been known as fructotransferases, so this is
CC       retained in the description (official name).
CC   -!- Since the transfer is intramolecular, the reaction is an elimination
CC       and, hence, the enzyme is a lyase, belonging in enzyme class 4.-.-.-.
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