2XLB

Acetyl xylan esterase from Bacillus pumilus without ligands


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.90 Å
  • R-Value Free: 0.150 
  • R-Value Work: 0.136 
  • R-Value Observed: 0.137 

wwPDB Validation   3D Report Full Report


This is version 1.1 of the entry. See complete history


Literature

The Crystal Structure of the Cephalosporin Deacetylating Enzyme Acetyl Xylan Esterase Bound to Paraoxon Explains the Low Sensitivity of This Serine Hydrolase to Organophosphate Inactivation.

Montoro-Garcia, S.Gil-Ortiz, F.Garcia-Carmona, F.Polo, L.M.Rubio, V.Sanchez-Ferrer, A.

(2011) Biochem J 436: 321

  • DOI: 10.1042/BJ20101859
  • Primary Citation of Related Structures:  
    2XLB, 2XLC

  • PubMed Abstract: 
  • Organophosphorus insecticides and nerve agents irreversibly inhibit serine hydrolase superfamily enzymes. One enzyme of this superfamily, the industrially important (for β-lactam antibiotic synthesis) AXE/CAH (acetyl xylan esterase/cephalosporin acetyl hydrolase) from the biotechnologically valuable organism Bacillus pumilus, exhibits low sensitivity to the organophosphate paraoxon (diethyl-p-nitrophenyl phosphate, also called paraoxon-ethyl), reflected in a high K(i) for it (~5 mM) and in a slow formation (t(½)~1 min) of the covalent adduct of the enzyme and for DEP (E-DEP, enzyme-diethyl phosphate, i ...

    Organophosphorus insecticides and nerve agents irreversibly inhibit serine hydrolase superfamily enzymes. One enzyme of this superfamily, the industrially important (for β-lactam antibiotic synthesis) AXE/CAH (acetyl xylan esterase/cephalosporin acetyl hydrolase) from the biotechnologically valuable organism Bacillus pumilus, exhibits low sensitivity to the organophosphate paraoxon (diethyl-p-nitrophenyl phosphate, also called paraoxon-ethyl), reflected in a high K(i) for it (~5 mM) and in a slow formation (t(½)~1 min) of the covalent adduct of the enzyme and for DEP (E-DEP, enzyme-diethyl phosphate, i.e. enzyme-paraoxon). The crystal structure of the E-DEP complex determined at 2.7 Å resolution (1 Å=0.1 nm) reveals strain in the active Ser¹⁸¹-bound organophosphate as a likely cause for the limited paraoxon sensitivity. The strain results from active-site-size limitation imposed by bulky conserved aromatic residues that may exclude as substrates esters having acyl groups larger than acetate. Interestingly, in the doughnut-like homohexamer of the enzyme, the six active sites are confined within a central chamber formed between two 60°-staggered trimers. The exclusive access to this chamber through a hole around the three-fold axis possibly limits the size of the xylan natural substrates. The enzyme provides a rigid scaffold for catalysis, as reflected in the lack of movement associated with paraoxon adduct formation, as revealed by comparing this adduct structure with that also determined in the present study at 1.9 Å resolution for the paraoxon-free enzyme.


    Organizational Affiliation

    Department of Biochemistry and Molecular Biology-A, Faculty of Biology, University of Murcia, Campus Espinardo, E-30100 Murcia, Spain.



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
ACETYL XYLAN ESTERASE
A, B, C, D, E, F, G, H, I, J, K, L
A, B, C, D, E, F, G, H, I, J, K, L
320Bacillus pumilusMutation(s): 0 
Gene Names: axe
EC: 3.1.1.72 (PDB Primary Data), 3.1.1.6 (UniProt)
UniProt
Find proteins for Q9K5F2 (Bacillus pumilus)
Explore Q9K5F2 
Go to UniProtKB:  Q9K5F2
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ9K5F2
Protein Feature View
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.90 Å
  • R-Value Free: 0.150 
  • R-Value Work: 0.136 
  • R-Value Observed: 0.137 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 143.477α = 90
b = 87.301β = 112.89
c = 184.291γ = 90
Software Package:
Software NamePurpose
REFMACrefinement
MOSFLMdata reduction
SCALAdata scaling
MOLREPphasing

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2011-05-25
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance