This entry represents and . These modules have a core structure consisting of a 3-stranded meander β-sheet, which contain six aromatic groups that may be important for binding. CBM5/12 is found in proteins such as chitinase A1, chitinase B [ PUBMED:10788483 ], and endoglucanase Z [ PUBMED:9405041 … expand

This entry represents and . These modules have a core structure consisting of a 3-stranded meander β-sheet, which contain six aromatic groups that may be important for binding. CBM5/12 is found in proteins such as chitinase A1, chitinase B [ PUBMED:10788483 ], and endoglucanase Z [ PUBMED:9405041 ].

The overall topology of the CBM is structurally similar to the C-terminal chitin-binding domains (ChBD) of chitinase A1 and chitinase B, however the binding mechanism for the ChBD may be different from that of the CBM [ PUBMED:10788483 ].

A carbohydrate-binding module (CBM) is defined as a contiguous amino acid sequence within a carbohydrate-active enzyme with a discreet fold having carbohydrate-binding activity. A few exceptions are CBMs in cellulosomal scaffolding proteins and rare instances of independent putative CBMs. The requirement of CBMs existing as modules within larger enzymes sets this class of carbohydrate-binding protein apart from other non-catalytic sugar binding proteins such as lectins and sugar transport proteins.

CBMs were previously classified as cellulose-binding domains (CBDs) based on the initial discovery of several modules that bound cellulose [ PUBMED:3338453 PUBMED:3134347 ]. However, additional modules in carbohydrate-active enzymes are continually being found that bind carbohydrates other than cellulose yet otherwise meet the CBM criteria, hence the need to reclassify these polypeptides using more inclusive terminology.

Previous classification of cellulose-binding domains were based on amino acid similarity. Groupings of CBDs were called "Types" and numbered with roman numerals (e.g. Type I or Type II CBDs). In keeping with the glycoside hydrolase classification, these groupings are now called families and numbered with Arabic numerals. Families 1 to 13 are the same as Types I to XIII. For a detailed review on the structure and binding modes of CBMs see [ PUBMED:15214846 ].