X25 domain of Bacillus acidopullulyticus pullulanase and similar proteins.
Pullulanase (EC 3.2.1.41) cleaves 1,6-alpha-glucosidic linkages in pullulan, amylopectin, and glycogen, and in alpha-and beta-amylase limit-dextrins of amylopectin and glycogen. BaPul is used industrially in the production of high fructose corn syrup, high maltose content syrups and low calorie and ''light'' beers. Pullulanases, in addition to the catalytic domain, include several carbohydrate-binding domains (CBMs) as well as domains of unknown function (termed ''X'' modules). X25 was identified in Bacillus acidopullulyticus pullulanase, and splits another domain of unknown function (X45). X25 is present in multiple copy in some pullulanases. It has been suggested that X25 and X45 are CBMs which target mixed alpha-1,6/alpha-1,4 linked D-glucan polysaccharides.
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