DB code: S00209

RLCP classification 1.30.36210.971 : Hydrolysis
CATH domain : TIM Barrel Catalytic domain
CSA 1aq0
M-CSA 1aq0

CATH domain Related DB codes (homologues) : TIM Barrel S00202 S00210 S00748 S00906 S00907 S00911 S00912 S00915 M00134 M00160 D00479 S00204 S00205 S00206 S00207 S00203 S00208 S00211 S00213 S00214 M00113 T00307 D00165 D00166 D00169 D00176 D00501 D00502 D00503 D00844 D00861 D00864 M00026 M00112 M00193 M00346 T00057 T00062 T00063 T00066 T00067

Uniprot Enzyme Name
UniprotKB Protein name Synonyms CAZy Pfam
P12257 Lichenase-2
Lichenase II
Endo-beta-1,3-1,4 glucanase II
Endo-beta-1,3-1,4 glucanase II) ((1->3,1->4)-beta-glucanase isoenzyme EII
GH17 (Glycoside Hydrolase Family 17)
PF00332 (Glyco_hydro_17)
[Graphical View]

KEGG enzyme name
beta-(1->4)-D-glucan 4-glucanohydrolase
1,4-beta-glucan endohydrolase
1,4-beta-glucan 4-glucanohydrolase
1,3-1,4-beta-D-glucan 4-glucanohydrolase

UniprotKB: Accession Number Entry name Activity Subunit Subcellular location Cofactor
P12257 GUB2_HORVU Hydrolysis of (1->4)-beta-D-glucosidic linkages in beta-D-glucans containing (1->3)- and (1->4)-bonds.

KEGG Pathways
Map code Pathways E.C.

Compound table
Substrates Products Intermediates
KEGG-id C00551 C00001 C00478 C00551
Compound beta-D-Glucan H2O Lichenin beta-D-Glucan
Type polysaccharide H2O carbohydrate polysaccharide
ChEBI 15377
PubChem 46173706
1aq0A Unbound Unbound Unbound
1aq0B Unbound Unbound Unbound
1ghrA Unbound Unbound Unbound

Reference for Active-site residues
resource references E.C.
see [Comments]

Active-site residues
PDB Catalytic residues Cofactor-binding residues Modified residues Main-chain involved in catalysis Comment
1aq0A GLU 93;TYR 170;GLU 232
1aq0B GLU 93;TYR 170;GLU 232
1ghrA GLU 93;TYR 170;GLU 232

References for Catalytic Mechanism
References Sections No. of steps in catalysis
p.Fig.2, p.648-650 4

Comments crystallization, preliminary X-ray diffraction analysis (1.8 angstroms)
Medline ID
PubMed ID 8254681
Journal J Mol Biol
Year 1993
Volume 234
Pages 888-9
Authors Chen L, Garrett TJ, Varghese JN, Fincher GB, Hoj PB
Title Crystallization and preliminary X-ray analysis of (1,3)- and (1,3;1,4)-beta-D-glucanases from germinating barley.
Related PDB
Related UniProtKB
Comments catalytic amino acids, evolution
Medline ID
PubMed ID 8514770
Journal J Biol Chem
Year 1993
Volume 268
Pages 13318-26
Authors Chen L, Fincher GB, Hoj PB
Title Evolution of polysaccharide hydrolase substrate specificity. Catalytic amino acids are conserved in barley 1,3-1,4- and 1,3-beta-glucanases.
Related PDB
Related UniProtKB
Comments X-ray crystallography (2.2 angstroms).
Medline ID 94195828
PubMed ID 8146192
Journal Proc Natl Acad Sci USA
Year 1994
Volume 91
Pages 2785-9
Authors Varghese JN, Garrett TPJ, Colman PM, Chen L, Hoej PB, Fincher GB
Title Three-dimensional structures of two plant beta-glucan endohydrolases with distinct substrate specificities.
Related PDB 1ghr
Related UniProtKB P12257
Medline ID
PubMed ID 7492591
Journal Biochim Biophys Acta
Year 1995
Volume 1253
Pages 112-6
Authors Chen L, Sadek M, Stone BA, Brownlee RT, Fincher GB, Hoj PB
Title Stereochemical course of glucan hydrolysis by barley (1-->3)- and (1-->3, 1-->4)-beta-glucanases.
Related PDB
Related UniProtKB
Comments Review
Medline ID
PubMed ID 9345622
Journal Curr Opin Struct Biol
Year 1997
Volume 7
Pages 645-51
Authors White A, Rose DR
Title Mechanism of catalysis by retaining beta-glycosyl hydrolases.
Related PDB
Related UniProtKB
Comments X-ray crystallography (2.0 angstroms).
Medline ID 98123117
PubMed ID 9452466
Journal J Biol Chem
Year 1998
Volume 273
Pages 3438-46
Authors Mueller JJ, Thomsen KK, Heinemann U
Title Crystal structure of barley 1,3-1,4-beta-glucanase at 2.0-A resolution and comparison with Bacillus 1,3-1,4-beta-glucanase.
Related PDB 1aq0
Related UniProtKB P12257
Medline ID
PubMed ID 12023973
Journal J Biol Chem
Year 2002
Volume 277
Pages 30102-11
Authors Hrmova M, Imai T, Rutten SJ, Fairweather JK, Pelosi L, Bulone V, Driguez H, Fincher GB
Title Mutated varley (1,3)-beta-D-glucan endohydrolases synthesize crystalline (1,3)-beta-D-glucans.
Related PDB
Related UniProtKB

This enzyme belongs to the family-17 of glycosidase enzymes, a member family of 4/7 superfamily, which has got the catalytic residues at the C-terminal ends of beta-4 and beta-7 on the (alpha/beta)8 barrel fold.
Glu232 has been reported to be the nucleophilic residue of this enzyme [2]. This paper [2] also suggested that Glu288 is likely to be the catalytic acid. However, another paper [7] suggested that Glu94 is most likely to be the catalytic acid/base. Comparing with other 4/7 superfamily enzymes, Glu288 is too distant from the nucleophile, Glu232. Thus, Glu94 must be the acid/base.
The literature [5] described general aspects of the catalytic mechanism of retaining beta-glycosyl hydrolases. Accoriding to the paper, the mechanism can be described as follows:
(1) Saccharide binds in a "twisted-boat" conformation.
(2) The beta-1,4 linkage is broken, leading to the formation of a transition state with a slight positive charge at the anomeric carbon, in a "half-chair" conformation, which develops a oxocarbenium-ion-like character.
(3) An approach of the ionic species to the catalytic nucleophile leads to the formation of a covalent intermediate of inverted alpha-configuration in a so-called chair conformation. The aglycon is released and a water molecule diffuses into the vicinity of the acidic residue as a general base.
(4) The covalent intermediate reactivates through an oxocarbenium-ion-like transition state. The general base abstracts a proton from the incoming water, which in turn carries out a nucleophilic attack on the C1 atom of the residual saccharide.
Moreover, comparing the structural data with that of xylanase (E.C. (D00479 in EzCatDB), Tyr170 might stabilize the leaving nucleophile, Glu232 in deglycosylation. On the other hand, Tyr170 might modulate the activity of the nucleophile, according to the data of the other homologous enzyme, beta-glucosidase (E.C. (S00205 in EzCatDB).

Created Updated
2003-02-03 2009-02-26