DB code: M00192

RLCP classification 1.30.5050.991 : Hydrolysis
CATH domain 1.50.10.10 : Glycosyltransferase Catalytic domain
2.60.40.710 : Immunoglobulin-like
2.60.40.30 : Immunoglobulin-like
2.60.40.290 : Immunoglobulin-like
E.C. 3.2.1.4
CSA 1js4
M-CSA 1js4
MACiE

CATH domain Related DB codes (homologues)
2.60.40.30 : Immunoglobulin-like M00124 M00134 M00129 M00136 M00149
2.60.40.710 : Immunoglobulin-like T00246
1.50.10.10 : Glycosyltransferase S00531 S00048 S00845 D00167 D00500 T00245 T00246
2.60.40.290 : Immunoglobulin-like M00219 D00479 D00502 D00504 M00026

Uniprot Enzyme Name
UniprotKB Protein name Synonyms CAZy Pfam
P26221 Endoglucanase E-4
EC 3.2.1.4
Endo-1,4-beta-glucanase E-4
Cellulase E-4
Cellulase E4
CBM2 (Carbohydrate-Binding Module Family 2)
CBM3 (Carbohydrate-Binding Module Family 3)
GH9 (Glycoside Hydrolase Family 9)
PF00553 (CBM_2)
PF00942 (CBM_3)
PF00041 (fn3)
PF00759 (Glyco_hydro_9)
[Graphical View]

KEGG enzyme name
cellulase
endo-1,4-beta-D-glucanase
beta-1,4-glucanase
beta-1,4-endoglucan hydrolase
celluase A
cellulosin AP
endoglucanase D
alkali cellulase
cellulase A 3
celludextrinase
9.5 cellulase
avicelase
pancellase SS
1,4-(1,3
1,4)-beta-D-glucan 4-glucanohydrolase

UniprotKB: Accession Number Entry name Activity Subunit Subcellular location Cofactor
P26221 GUN4_THEFU Endohydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans.

KEGG Pathways
Map code Pathways E.C.
MAP00500 Starch and sucrose metabolism

Compound table
Substrates Products Intermediates
KEGG-id C00760 C00001 C00478 C00551 C00185 C00760
E.C.
Compound Cellulose H2O Lichenin beta-D-Glucan Cellobiose Cellulose
Type polysaccharide H2O carbohydrate polysaccharide polysaccharide polysaccharide
ChEBI 15377
 15377
 		17057
 17057
PubChem 22247451
 962
 22247451
 962
 		439241
 439241
 		46173706
 46173706
 		439178
 439178
1js4A01 Unbound Unbound Unbound Unbound Analogue:GLC-GLC-GLC
1js4B01 Unbound Unbound Unbound Analogue:GLC Analogue:GLC-GLC
1tf4A01 Unbound Unbound Unbound Unbound Unbound
1tf4B01 Unbound Unbound Unbound Unbound Unbound
3tf4A01 Unbound Unbound Unbound Analogue:GLC Analogue:GLC-GLC-GLC
3tf4B01 Unbound Unbound Unbound Analogue:GLC Analogue:GLC-GLC-GLC
4tf4A01 Unbound Unbound Unbound Analogue:GLC-GLC Analogue:GLC-GLC-GLC-GLC
4tf4B01 Unbound Unbound Unbound Analogue:GLC-GLC Analogue:GLC-GLC-GLC-GLC
1js4A02 Unbound Unbound Unbound Unbound Unbound
1js4B02 Unbound Unbound Unbound Unbound Unbound
1tf4A02 Unbound Unbound Unbound Unbound Unbound
1tf4B02 Unbound Unbound Unbound Unbound Unbound
3tf4A02 Unbound Unbound Unbound Unbound Unbound
3tf4B02 Unbound Unbound Unbound Unbound Unbound
4tf4A02 Unbound Unbound Unbound Unbound Unbound
4tf4B02 Unbound Unbound Unbound Unbound Unbound

Reference for Active-site residues
resource references E.C.
literature [2], [4]

Active-site residues
PDB Catalytic residues Cofactor-binding residues Modified residues Main-chain involved in catalysis Comment
1js4A01 ASP 55;ASP 58;HIS 125;TYR 206;GLU 424
1js4B01 ASP 55;ASP 58;HIS 125;TYR 206;GLU 424
1tf4A01 ASP 55;ASP 58;HIS 125;TYR 206;GLU 424
1tf4B01 ASP 55;ASP 58;HIS 125;TYR 206;GLU 424
3tf4A01 ASP 55;ASP 58;HIS 125;TYR 206;GLU 424
3tf4B01 ASP 55;ASP 58;HIS 125;TYR 206;GLU 424
4tf4A01 ASP 55;ASP 58;HIS 125;TYR 206;GLU 424
4tf4B01 ASP 55;ASP 58;HIS 125;TYR 206;GLU 424
1js4A02
1js4B02
1tf4A02
1tf4B02
3tf4A02
3tf4B02
4tf4A02
4tf4B02

References for Catalytic Mechanism
References Sections No. of steps in catalysis
[2]
Fig.4, p.814-815
[4]
p.9662

References
[1]
Resource
Comments
Medline ID
PubMed ID 8555231
Journal Biochemistry
Year 1996
Volume 35
Pages 586-92
Authors Barr BK, Hsieh YL, Ganem B, Wilson DB
Title Identification of two functionally different classes of exocellulases.
Related PDB
Related UniProtKB
[2]
Resource
Comments X-RAY CRYSTALLOGRAPHY (1.9 ANGSTROMS) OF 47-651
Medline ID 9334746
PubMed ID 9334746
Journal Nat Struct Biol
Year 1997
Volume 4
Pages 810-8
Authors Sakon J, Irwin D, Wilson DB, Karplus PA
Title Structure and mechanism of endo/exocellulase E4 from Thermomonospora fusca.
Related PDB 1js4 1tf4 3tf4 4tf4
Related UniProtKB P26221
[3]
Resource
Comments
Medline ID
PubMed ID 9537366
Journal J Bacteriol
Year 1998
Volume 180
Pages 1709-14
Authors Irwin D, Shin DH, Zhang S, Barr BK, Sakon J, Karplus PA, Wilson DB
Title Roles of the catalytic domain and two cellulose binding domains of Thermomonospora fusca E4 in cellulose hydrolysis.
Related PDB
Related UniProtKB
[4]
Resource
Comments
Medline ID
PubMed ID 15274620
Journal Biochemistry
Year 2004
Volume 43
Pages 9655-63
Authors Zhou W, Irwin DC, Escovar-Kousen J, Wilson DB
Title Kinetic studies of Thermobifida fusca Cel9A active site mutant enzymes.
Related PDB
Related UniProtKB

Comments
This enzyme belongs to the glycosidase family-9.
Although this enzyme binds two calcium ions, they are not involved in catalysis at all.
According to the literature [2], this enzyme hydrolyzes cellulose with inversion of configuration at the anomeric carbon. The reaction mechanism of this enzyme requires a general acid to protonate the glycosidic oxygen and a general base to extract a proton from a nucleophilic water which attacks the anomeric carbon.
The catalytic mechanism seems to be similar to that of beta-amylase (D00166 in EzCatDB). The reaction proceeds as follows (see [2] & [4]):
(0) Tyr206 modulates the pKa of Asp55, whereas His125 modulates the pKa of Asp58.
(1) Glu424 acts as a general acid to protonate the leaving group, the glycosidic oxygen, forming an oxocarbonium ion in the transition state. (SN1-like reaction)
(2) Both Asp55 and Asp58 act as general bases to deprotonate the nucleophilic water. (Here, Asp58 seems more likely to be the base.)
(3) The activated water makes a nucleophilic attack on the anomeric carbon to complete the reaction.

Created Updated
2004-03-23 2009-02-26