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The structure and characterization of a modular endo-beta-1,4-mannanase from Cellulomonas fimi

In English

Författare

Summary, in English

The endo-beta-1,4-mannanase from the soil bacterium Cellulomonas fimi is a modular plant cell wall degrading enzyme involved in the hydrolysis of the backbone of mannan, one of the most abundant polysaccharides of the hemicellulosic network in the plant cell wall. The crystal structure of a recombinant truncated endo-beta-1,4-mannanase from C. fimi (CMan26A-50K) was determined by X-ray crystallography to 2.25 angstrom resolution using the molecular replacement technique. The overall structure of the enzyme consists of a core (beta/alpha)(8)-barrel catalytic module characteristic of clan GH-A, connected via a linker to an immunoglobulin-like module of unknown function. A complex with the oligosaccharide mannotriose to 2.9 angstrom resolution has also been obtained. Both the native structure and the complex show a cacodylate ion bound at the -1 subsite, while subsites -2, -3, and -4 are occupied by mannotriose in the complex. Enzyme kinetic analysis and the analysis of hydrolysis products from manno-oligosaccharides and mannopentitol suggest five important active-site cleft subsites. CfMan26A-50K has a high affinity -3 subsite with Phe325 as an aromatic platform, which explains the mannose releasing property of the enzyme. Structural differences with the homologous Cellvibrio japonicus beta-1,4-mannanase (CjMan26A) at the -2 and -3 subsites may explain the poor performance of CfMan26A mutants as "glycosynthases".

Publiceringsår

2005

Språk

Engelska

Sidor

12700-12708

Publikation/Tidskrift/Serie

Biochemistry

Volym

44

Issue

38

Dokumenttyp

Artikel i tidskrift

Förlag

The American Chemical Society (ACS)

Ämne

  • Biochemistry and Molecular Biology

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 0006-2960