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Sammanfattning

As part of an ongoing enzyme discovery program to investigate the properties and catalytic mechanism of glycoside hydrolase family 12 (GH 12) endoglucanases, a GH family that contains several cellulases that are of interest in industrial applications, we have solved four new crystal structures of wild-type Humicola grisea Cel12A in complexes formed by soaking with cellobiose, cellotetraose, cellopentaose, and a thio-linked cellotetraose derivative (G(2)SG(2)). These complex structures allow mapping of the non-covalent interactions between the enzyme and the glucosyl chain bound in subsites -4 to +2 of the enzyme, and shed light on the mechanism and function of GH 12 cellulases. The unhydrolysed cellopentaose and the G2SG2 cello-oligomers span the active site of the catalytically active H. grisea Cel12A enzyme, with the pyranoside bound in subsite -1 displaying a S-1(3) skew boat conformation. After soaking in cellotetraose, the cello-oligomer that is found bound in site -4 to -1 contains a beta-1,3-linkage between the two cellobiose units in the oligomer, which is believed to have been formed by a transglycosylation reaction that has occurred during the ligand soak of the protein crystals. The close fit of this ligand and the binding sites occupied suggest a novel mixed beta-glucanase activity for this enzyme. (C) 2004 Elsevier Ltd. All rights reserved.

Nyckelord

cellulase; cellulose; endoglucanase; substrate complex; crystal structure

Publicerad i

Journal of Molecular Biology
2004, volym: 342, nummer: 5, sidor: 1505-1517
Utgivare: ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD

SLU författare

UKÄ forskningsämne

Molekylärbiologi

Publikationens identifierare

  • DOI: https://doi.org/10.1016/j.jmb.2004.07.098

Permanent länk till denna sida (URI)

https://res.slu.se/id/publ/3263