The enzyme catalyses the sequential degradation of (1->4)-alpha-D-glucans from the non-reducing end with the release of 1,5-anhydro-D-fructose. Thus, for an alpha-glucan containing n (1->4)-linked glucose units, the final products are 1 glucose plus (n-1) 1,5-anhydro-D-fructose. Maltose, maltosaccharides and amylose are all completely degraded. It does not degrade (1->6)-alpha-glucosidic bonds and thus the degradation of a branched glucan, such as amylopectin or glycogen, will result in the formation of 1,5-anhydro-D-fructose plus a limit dextrin. Other enzymes involved in the anhydrofructose pathway are EC 188.8.131.52 (aldos-2-ulose dehydratase), EC 184.108.40.206 (1,5-anhydro-D-fructose dehydratase) and EC 220.127.116.11 (ascopyrone tautomerase).