Carbohydrate Binding Module Family 82

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• Author: ^^^Darrell Cockburn^^^
• Responsible Curator: ^^^Nicole Koropatkin^^^

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CAZy DB link

https://www.cazy.org/CBM82.html

Figure 1. Domain architecture of E. rectale Amy13K The CBM and GH families are noted. The 'S' indicate the signal sequence and the 'anchor' is a cell wall anchor region. The unknown domain has no known function, however, deletion eliminates enzyme activity [1].

Ligand specificities

The founding member of this family and the first module to be characterized is the first CBM found in the cell-wall anchored Amy13K from Eubacterium rectale (see Fig1). It was found to bind beta-cyclodextrin and glycogen with similar affinity, with slightly weaker affinity for maltoheptaose as determined by isothermal titration calorimetry. The module was also found to bind to corn starch granules, both from a wild-type source and from a high amylose source (HiMaize 260) with approximately equal affinity but did not demonstrate binding to potato starch or a chemically crosslinked starch (Fibersym) as determined via depletion assays. Binding to amylopectin and pullulan was also demonstrated via affinity electrophoresis. [1].

Structural Features

There is currently no structure solved for this family, however, secondary structure analysis and alignments suggest they are likely to be beta-sandwich type folds similar to the CBM41 family.

Functionalities

This family has been found to be exclusively associated with GH13 family amylases from a quite narrow taxonomic range within Roseburia and Eubacterium rectale. Removal of the only CBM82 from the E. rectale Amy13K enzyme resulted in an approximately 2-fold decrease in activity of the enzyme towards amylopectin or potato starch, but resulted in a larger 5-fold decrease in the activity of the enzyme towards corn starch granules, suggesting an important role in targeting the enzyme to this substrate. [1]

Family Firsts

First Identified

In Roseburia inulinivorans as a predicted CBM [2]

First Characterized

From E. rectale Amy13K, establishing the family [1]

References

1. Cockburn DW, Suh C, Medina KP, Duvall RM, Wawrzak Z, Henrissat B, and Koropatkin NM. (2018). Novel carbohydrate binding modules in the surface anchored α-amylase of Eubacterium rectale provide a molecular rationale for the range of starches used by this organism in the human gut. Mol Microbiol. 2018;107(2):249-264. DOI:10.1111/mmi.13881 |
2. Ramsay AG, Scott KP, Martin JC, Rincon MT, and Flint HJ. (2006). Cell-associated alpha-amylases of butyrate-producing Firmicute bacteria from the human colon. Microbiology (Reading). 2006;152(Pt 11):3281-3290. DOI:10.1099/mic.0.29233-0 |