DB code: S00208

RLCP classification	1.30.35885.972 : Hydrolysis
CATH domain	3.20.20.80 : TIM Barrel	Catalytic domain
E.C.	3.2.1.58
CSA	1cz1
M-CSA	1cz1
MACiE

CATH domain	Related DB codes (homologues)
3.20.20.80 : TIM Barrel	S00202 S00210 S00748 S00906 S00907 S00911 S00912 S00915 M00134 M00160 D00479 S00204 S00205 S00206 S00207 S00203 S00209 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	RefSeq	CAZy	Pfam
P29717	Glucan 1,3-beta-glucosidase	EC 3.2.1.58 Exo-1,3-beta-glucanase	XP_721488.1 (Protein) XM_716395.1 (DNA/RNA sequence)	GH5 (Glycoside Hydrolase Family 5)	PF00150 (Cellulase) [Graphical View]

KEGG enzyme name
glucan 1,3-beta-glucosidase exo-1,3-beta-glucosidase beta-1,3-glucan exo-hydrolase exo (1->3)-glucanohydrolase 1,3-beta-glucan glucohydrolase

UniprotKB: Accession Number	Entry name	Activity	Subunit	Subcellular location	Cofactor
P29717	EXG_CANAL	Successive hydrolysis of beta-D-glucose units from the non-reducing ends of (1->3)-beta-D-glucans, releasing alpha-glucose.	Monomer.	Secreted.

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

Compound table
	Substrates			Products		Intermediates
KEGG-id	C00965	C00001	C02048	C00965	C00267	I00119
E.C.
Compound	1,3-beta-D-Glucan	H2O	Laminaribiose	1,3-beta-D-Glucan	alpha-D-Glucose	Peptidyl-Glu-1,3-beta-D-glucan	Transition state in deglycosylation
Type	polysaccharide	H2O	polysaccharide	polysaccharide	carbohydrate
ChEBI		15377 15377	18411 18411		17925 17925
PubChem		22247451 962 22247451 962	439637 439637		79025 79025

1cz1A	Unbound		Unbound	Unbound	Unbound	Unbound	Unbound
1eqcA	Unbound		Unbound	Unbound	Unbound	Unbound	Transition-state-analogue:CTS
1eqpA	Unbound		Unbound	Unbound	Unbound	Unbound	Unbound

Reference for Active-site residues
resource	references	E.C.
Swiss-prot;P29717 (see [Comments])

Active-site residues
PDB	Catalytic residues	Cofactor-binding residues	Modified residues	Main-chain involved in catalysis	Comment

1cz1A	ARG 92;ASN 191;GLU 192;HIS 253;TYR 255;GLU 292
1eqcA	ARG 92;ASN 191;GLU 192;HIS 253;TYR 255;GLU 292
1eqpA	ARG 92;ASN 191;GLU 192;HIS 253;TYR 255;GLU 292

References for Catalytic Mechanism
References	Sections	No. of steps in catalysis
[2]	Scheme 1	4
[3]	Fig.2, p.648-649	4
[4]	Fig.1, p.779-780

References
[1]
Resource
Comments	crystallization, diffraction (1.9 angstroms)
Medline ID
PubMed ID	1583691
Journal	J Mol Biol
Year	1992
Volume	225
Pages	217-8
Authors	Cutfield S, Brooke G, Sullivan P, Cutfield J
Title	Crystallization of the exo(1,3)-beta-glucanase from Candida albicans.
Related PDB
Related UniProtKB
[2]
Resource
Comments	Active site glu-330.
Medline ID	97166150
PubMed ID	9013549
Journal	J Biol Chem
Year	1997
Volume	272
Pages	3161-7
Authors	MacKenzie LF, Brooke GS, Cutfield JF, Sullivan PA, Withers SG
Title	Identification of Glu-330 as the catalytic nucleophile of Candida albicans exo-beta-(1,3)-glucanase.
Related PDB
Related UniProtKB	P29717
[3]
Resource
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
[4]
Resource
Comments	X-ray crystallography (1.85 angstroms) of 45-438.
Medline ID	20079533
PubMed ID	10610795
Journal	J Mol Biol
Year	1999
Volume	294
Pages	771-83
Authors	Cutfield SM, Davies GJ, Murshudov G, Anderson BF, Moody PC, Sullivan PA, Cutfield JF
Title	The structure of the exo-beta-(1,3)-glucanase from Candida albicans in native and bound forms: relationship between a pocket and groove in family 5 glycosyl hydrolases.
Related PDB	1cz1 1eqc
Related UniProtKB	P29717
[5]
Resource
Comments	crystal structure
Medline ID
PubMed ID	11112513
Journal	Protein Eng
Year	2000
Volume	13
Pages	735-8
Authors	Cutfield JF, Sullivan PA, Cutfield SM
Title	Minor Structural Consequences of the Alternative Cug Codon Usage (Ser for Leu) in Candida Albicans Exoglucanase.
Related PDB	1eqp
Related UniProtKB

Comments
This enzyme belongs to the glycosidase family-5. The paper [3] 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. 3.2.1.8) (D00479 in EzCatDB) and the other family-5 enzyme, cellulase (E.C. 3.2.1.4) (S00203 in EzCatDB), Tyr255 might stabilize the leaving nucleophile, Glu292 in deglycosylation, whilst His253 might modulate the activity of Glu192. On the other hand, Tyr255 might modulate the activity of the nucleophile, according to the data of the other homologous enzyme, beta-glucosidase (E.C. 3.2.1.21) (S00205 in EzCatDB).

Comments

This enzyme belongs to the glycosidase family-5.
The paper [3] 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. 3.2.1.8) (D00479 in EzCatDB) and the other family-5 enzyme, cellulase (E.C. 3.2.1.4) (S00203 in EzCatDB), Tyr255 might stabilize the leaving nucleophile, Glu292 in deglycosylation, whilst His253 might modulate the activity of Glu192. On the other hand, Tyr255 might modulate the activity of the nucleophile, according to the data of the other homologous enzyme, beta-glucosidase (E.C. 3.2.1.21) (S00205 in EzCatDB).

Created	Updated
2003-02-03	2012-02-14