Family 46 Carbohydrate-binding Modules Contribute to the Enzymatic Hydrolysis of Xyloglucan and β-1,3–1,4-Glucans through Distinct Mechanisms

Abstract

Background: CBMs are, generally, functionally and structurally autonomous from their associated catalytic domains. Results: The structure of a novel cellulase, BhCel5B, reveals that the appended carbohydrate-binding module, CBM46, extends the enzyme catalytic cleft. Conclusion: CBM46 targets BhCel5B to xyloglucan and is part of the catalytic cleft required for the hydrolysis of ␤-1,3-1,4-glucans. Significance: CBM46 has a dual role in the hydrolysis of complex carbohydrates by BhCel5B.

Structural Insights into the Broad Substrate Specificity of a Novel Endoglycoceramidase I Belonging to a New Subfamily of GH5 Glycosidases

“…The ␤-sandwich domain may not be involved in binding the carbohydrate portion of the substrate, because it located on the opposite face of the (␣/␤) 8 domain. Similar domains have been observed in other GH5 family members, including M777_ EGCase II (16), endo-xyloglucanase (25), and ␤-glucanase (26). Indeed, many of these carbohydrate-binding modules do not bind the substrate independently (27).…”

Reassembly and co-crystallization of a family 9 processive endoglucanase from its component parts: Structural and functional significance of the intermodular linker

“…In addition to the Cel9 CBM3c, several other examples of CBMs that are considered to modulate catalytic specificity and act cooperatively with the catalytic domain have recently been discovered. These include CBM66 that directs the cognate enzyme towards highly branched glucans rather than linear fructose polymers (Cuskin et al 2012), CBM48 that contributes to substrate binding at the active site of a glucan phosphatase (Meekins et al 2014), family-43 β-xylosidases where the GH43 is complemented by an additional module that confers hydrolytic activity to the mature enzyme (Moraïs et al 2012), and CBM46, that constitutes part of the catalytic cleft required for the hydrolysis of β-1,3-1,4-glucans (Venditto et al 2015). The carbohydrate-binding PA14 domain is also known to affect substrate binding of the catalytic domain by contributing to the formation of its active site (Gruninger et al 2014;Zmudka et al 2013).…”

Peer Review #1 of "Reassembly and co-crystallization of a family 9 processive endoglucanase from its component parts: structural and functional significance of the intermodular linker (v0.1)"

“…xylosidases where the GH43 is complemented by an additional module that confers hydrolytic activity to the mature enzyme (Moraïs et al 2012), and CBM46, that constitutes part of the catalytic cleft required for the hydrolysis of β-1,3-1,4-glucans (Venditto et al 2015). The carbohydrate-binding PA14 domain is also known to affect substrate binding of the catalytic domain by contributing to the formation of its active site (Gruninger et al 2014;Zmudka et al 2013).…”