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Three-dimensional crystal structure and enzymic characterization of beta-mannanase Man5A from blue mussel Mytilus edulis

Författare:
Publiceringsår: 2006
Språk: Engelska
Sidor: 1500-1510
Publikation/Tidskrift/Serie: Journal of Molecular Biology
Volym: 357
Nummer: 5
Dokumenttyp: Artikel
Förlag: Elsevier Science Ltd

Sammanfattning

Endo-beta-1,4-D-mannanase is the key depolymerizing enzyme for beta-1,4-mannan polymers present in the cell walls of plants and some algae, as well as in some types of plant seeds. Endo-1,4-beta-mannanase from blue mussel Mytilus edulis (MeMan5A) belongs to the glycoside hydrolase (GH) family 5 enzymes. The MeMan5A structure has been determined to 1.6 angstrom resolution using the multiple-wavelength anomalous dispersion method at the selenium K edge with selenomethionyl MeMan5A expressed in the yeast Pichia pastoris. As expected for GH 5 enzymes, the structure showed a (beta alpha)(8)-barrel fold. An unusually large number of histidine side-chains are exposed on the surface, which may relate to its location within the crystalline style of the digestive tract of the mussel. Kinetic analysis of MeMan5A revealed that the enzyme requires at least six subsites for efficient hydrolysis. Mannotetraose (M4) and mannopentaose (M5) were shown to interact with subsites -3 to +1, and -3 to +2, respectively. A clear kinetic threshold was observed when going from M4 to M5, indicating that the +2 subsite provides important interaction in the hydrolysis of short oligomeric mannose substrates. The catalytic centre motif at subsite -1 found in superfamily GH clan A is, as expected, conserved in MeMan5A, but the architecture of the catalytic cleft differs significantly from other GH 5 enzyme structures. We therefore suggest that MeMan5A represents a new subfamily in GH 5. (c) 2006 Elsevier Ltd. All rights reserved.

Disputation

Nyckelord

  • Biology and Life Sciences
  • Pichia pastoris
  • SeMet
  • mannanase
  • Mytilus edulis
  • MAD

Övriga

Published
Yes
  • ISSN: 0022-2836

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