Licheninase (glycosyl hydrolase 16 family)

 

These retaining glysocidases catalyse the hydrolysis of (1->4)-beta-D-glucosidic linkages in beta-D-glucans containing (1->3)- and (1->4)-bonds. They belong to glycosyl hydrolase 16 family.

 

Reference Protein and Structure

Sequence
P23904 UniProt (3.2.1.73) IPR008264 (Sequence Homologues) (PDB Homologues)
Biological species
Paenibacillus macerans (Bacteria) Uniprot
PDB
2ayh - CRYSTAL AND MOLECULAR STRUCTURE AT 1.6 ANGSTROMS RESOLUTION OF THE HYBRID BACILLUS ENDO-1,3-1,4-BETA-D-GLUCAN 4-GLUCANOHYDROLASE H(A16-M) (1.6 Å) PDBe PDBsum 2ayh
Catalytic CATH Domains
2.60.120.200 CATHdb (see all for 2ayh)
Click To Show Structure

Enzyme Reaction (EC:3.2.1.73)

alpha-maltose
CHEBI:18167ChEBI
+
water
CHEBI:15377ChEBI
→
alpha-D-glucose
CHEBI:17925ChEBI
+
alpha-D-glucose
CHEBI:17925ChEBI
Alternative enzyme names: 1,3;1,4-beta-glucan 4-glucanohydrolase, 1,3;1,4-beta-glucan endohydrolase, Beta-(1->3), (1->4)-D-glucan 4-glucanohydrolase, Lichenase, Endo-beta-1,3-1,4 glucanase, Mixed linkage beta-glucanase, Beta-glucanase, 1,3-1,4-beta-D-glucan 4-glucanohydrolase,

Enzyme Mechanism

Introduction

This is a retaining glycosidase enzyme, thus the stereochemistry of the anomeric carbon of the sugar product is retained. Glu105 initiates a nuclephilic attack on the anomieric carbon forming a covalent glycosyl-enzyme intermediate through an oxocarbonium-like transition-state. At the same time, Glu109 assists this step as a general acid, to protonate the scissile glycosidic oxygen. Glu102 acts as a general acid, to activate a water molecule, which then makes a nucleophilic attack on teh anomieric carbon, resulting in product release and regeneration of the active site. The second step also proceeds via an oxocarbonium-like transition-state.

Catalytic Residues Roles

UniProt PDB* (2ayh)
Glu128 Glu105A Acts as the catalytic nucleophile during the course of the reaction. covalent catalysis
Glu132 Glu109A Acts as a general acid/base. proton shuttle (general acid/base)
*PDB label guide - RESx(y)B(C) - RES: Residue Name; x: Residue ID in PDB file; y: Residue ID in PDB sequence if different from PDB file; B: PDB Chain; C: Biological Assembly Chain if different from PDB. If label is "Not Found" it means this residue is not found in the reference PDB.

Chemical Components

References

  1. Biarnés X et al. (2011), J Am Chem Soc, 133, 20301-20309. Catalytic itinerary in 1,3-1,4-β-glucanase unraveled by QM/MM metadynamics. Charge is not yet fully developed at the oxocarbenium ion-like transition state. DOI:10.1021/ja207113e. PMID:22044419.
  2. Biarnés X et al. (2006), J Biol Chem, 281, 1432-1441. Substrate distortion in the Michaelis complex of Bacillus 1,3-1,4-beta-glucanase. Insight from first principles molecular dynamics simulations. DOI:10.1074/jbc.M507643200. PMID:16260784.
  3. Planas A (2000), Biochim Biophys Acta, 1543, 361-382. Bacterial 1,3-1,4-beta-glucanases: structure, function and protein engineering. PMID:11150614.
  4. Viladot JL et al. (1998), Biochemistry, 37, 11332-11342. Probing the mechanism of Bacillus 1,3-1,4-beta-D-glucan 4-glucanohydrolases by chemical rescue of inactive mutants at catalytically essential residues. DOI:10.1021/bi980586q. PMID:9698381.
  5. Malet C et al. (1997), Biochemistry, 36, 13838-13848. Mechanism of Bacillus 1,3-1,4-beta-D-glucan 4-glucanohydrolases: kinetics and pH studies with 4-methylumbelliferyl beta-D-glucan oligosaccharides. DOI:10.1021/bi9711341. PMID:9374861.
  6. Hahn M et al. (1995), J Biol Chem, 270, 3081-3088. Crystal structure and site-directed mutagenesis of Bacillus macerans endo-1,3-1,4-beta-glucanase. PMID:7852389.
  7. Juncosa M et al. (1994), J Biol Chem, 269, 14530-14535. Identification of active site carboxylic residues in Bacillus licheniformis 1,3-1,4-beta-D-glucan 4-glucanohydrolase by site-directed mutagenesis. PMID:8182059.
  8. Høj PB et al. (1992), J Biol Chem, 267, 25059-25066. Identification of glutamic acid 105 at the active site of Bacillus amyloliquefaciens 1,3-1,4-beta-D-glucan 4-glucanohydrolase using epoxide-based inhibitors. PMID:1360982.

Step 1.

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Catalytic Residues Roles

Residue Roles
Glu105A covalent catalysis
Glu109A proton shuttle (general acid/base)

Chemical Components

Step 1.

Contributors

Craig Porter, Gemma L. Holliday