PDBsum entry 2cc0

Hydrolase

PDB id: 2cc0

Contents

Protein chains

192 a.a. *

Ligands

ACT ×2

Metals

_ZN ×2

Waters ×564

* Residue conservation analysis

PDB id:

2cc0

Name:

Hydrolase

Title:

Family 4 carbohydrate esterase from streptomyces lividans in complex with acetate

Structure:

Acetyl-xylan esterase. Chain: a, b. Fragment: residues 42-236. Synonym: carbohydrate esterase. Engineered: yes

Source:

Streptomyces lividans. Organism_taxid: 1916. Expressed in: streptomyces lividans. Expression_system_taxid: 1916

Biol. unit:

Dimer (from PDB file)

Resolution:

1.60Å R-factor: 0.152 R-free: 0.188

Authors:

E.J.Taylor,T.M.Gloster,J.P.Turkenburg,F.Vincent,A.M.Brzozowski, C.Dupont,F.Shareck,M.S.J.Centeno,J.A.M.Prates,V.Puchart, L.M.A.Ferreira,C.M.G.A.Fontes,P.Biely,G.J.Davies

Key ref:

E.J.Taylor et al. (2006). Structure and activity of two metal ion-dependent acetylxylan esterases involved in plant cell wall degradation reveals a close similarity to peptidoglycan deacetylases. J Biol Chem, 281, 10968-10975. PubMed id: 16431911 DOI: 10.1074/jbc.M513066200

Date:

10-Jan-06 Release date: 23-Jan-06

Protein chains

Q54413  (Q54413_STRLI) -  Acetyl-xylan esterase from Streptomyces lividans

Seq: 335 a.a.

Struc: 192 a.a.

Enzyme reactions

• Enzyme class: E.C.3.1.1.72 - acetylxylan esterase.
• Reaction: Deacetylation of xylans and xylo-oligosaccharides.

DOI no: 10.1074/jbc.M513066200

J Biol Chem 281:10968-10975 (2006)

PubMed id: 16431911

Structure and activity of two metal ion-dependent acetylxylan esterases involved in plant cell wall degradation reveals a close similarity to peptidoglycan deacetylases.

E.J.Taylor, T.M.Gloster, J.P.Turkenburg, F.Vincent, A.M.Brzozowski, C.Dupont, F.Shareck, M.S.Centeno, J.A.Prates, V.Puchart, L.M.Ferreira, C.M.Fontes, P.Biely, G.J.Davies.

ABSTRACT

The enzymatic degradation of plant cell wall xylan requires the concerted action of a diverse enzymatic syndicate. Among these enzymes are xylan esterases, which hydrolyze the O-acetyl substituents, primarily at the O-2 position of the xylan backbone. All acetylxylan esterase structures described previously display a alpha/beta hydrolase fold with a "Ser-His-Asp" catalytic triad. Here we report the structures of two distinct acetylxylan esterases, those from Streptomyces lividans and Clostridium thermocellum, in native and complex forms, with x-ray data to between 1.6 and 1.0 A resolution. We show, using a novel linked assay system with PNP-2-O-acetylxyloside and a beta-xylosidase, that the enzymes are sugar-specific and metal ion-dependent and possess a single metal center with a chemical preference for Co2+. Asp and His side chains complete the catalytic machinery. Different metal ion preferences for the two enzymes may reflect the surprising diversity with which the metal ion coordinates residues and ligands in the active center environment of the S. lividans and C. thermocellum enzymes. These "CE4" esterases involved in plant cell wall degradation are shown to be closely related to the de-N-acetylases involved in chitin and peptidoglycan degradation (Blair, D. E., Schuettelkopf, A. W., MacRae, J. I., and Aalten, D. M. (2005) Proc. Natl. Acad. Sci. U. S. A., 102, 15429-15434), which form the NodB deacetylase "superfamily."

Selected figure(s)

Figure 4.
FIGURE 4. Comparison of the S. lividans acetylxylan esterase, SlCE4, and the peptidoglycan deacetylase from S. pneumonia. A, ribbon representation of SlCE4 (green) overlapped with the peptidoglycan de-N-acetylase from S. pneumonia (purple). Active site residues and acetate molecules (gray) are shown in ball-and-stick representation and Zn^2+ ions as spheres. B, divergent stereo ball-and-stick representation of SlCE4 active site residues (green) overlapped with those from the peptidoglycan de-N-acetylase from S. pneumonia (purple and labeled); the acetate molecules are shown in green/gray. Zn^2+ ions (cyan) and water molecules are shown as spheres. Figures were made using MOLSCRIPT (44, 45) and rendered using RASTER3D (46).

Figure 7.
FIGURE 7. Active site interactions and catalysis in family CE4 acetylxylan esterases. Schematic diagram of the metal ion coordination of the S. lividans family CE4 esterase (acetate shown in red)(A) and the C. thermocellum CE4 esterase (B) and a putative reaction mechanism (C) based upon classical Zn^2+ hydrolase chemistry and the work of van Aalten and colleagues (19) on the streptococcal peptidoglycan deacetylases. The divalent metal plays the role of Lewis acid, with Asp and His residues playing the roles of catalytic base (activating the nucleophilic water) and acid (aiding sugar departure).

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2006, 281, 10968-10975) copyright 2006.

Figures were selected by an automated process.