DB code: S00207

RLCP classification	1.30.36210.971 : Hydrolysis
CATH domain	3.20.20.80 : TIM Barrel	Catalytic domain
E.C.	3.2.1.39
CSA	1ghs
M-CSA	1ghs
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 S00203 S00208 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	CAZy	Pfam
P15737	Glucan endo-1,3-beta-glucosidase GII	EC 3.2.1.39 EC 3.2.1.39) ((1->3)-beta-glucan endohydrolase GII 1->3)-beta-glucan endohydrolase GII) ((1->3)-beta-glucanase isoenzyme GII Beta-1,3-endoglucanase GII	GH17 (Glycoside Hydrolase Family 17)	PF00332 (Glyco_hydro_17) [Graphical View]

KEGG enzyme name
glucan endo-1,3-beta-D-glucosidase endo-1,3-beta-glucanase laminarinase laminaranase oligo-1,3-glucosidase endo-1,3-beta-glucanase callase beta-1,3-glucanase kitalase 1,3-beta-D-glucan 3-glucanohydrolase endo-(1,3)-beta-D-glucanase (1->3)-beta-glucan 3-glucanohydrolase endo-1,3-beta-D-glucanase endo-1,3-beta-glucosidase 1,3-beta-D-glucan glucanohydrolase

UniprotKB: Accession Number	Entry name	Activity	Subunit	Subcellular location	Cofactor
P15737	E13B_HORVU	Hydrolysis of (1->3)-beta-D-glucosidic linkages in (1->3)-beta-D-glucans.

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

Compound table
	Substrates			Products	Intermediates
KEGG-id	C00965	C00001	C00771	C00965
E.C.
Compound	1,3-beta-D-Glucan	H2O	Laminarin	1,3-beta-D-Glucan
Type	polysaccharide	H2O	polysaccharide	polysaccharide
ChEBI		15377 15377
PubChem		22247451 962 22247451 962	46173707 46173707

1ghsA	Unbound		Unbound	Unbound
1ghsB	Unbound		Unbound	Unbound

Reference for Active-site residues
resource	references	E.C.

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

1ghsA	GLU 94;TYR 168;GLU 231
1ghsB	GLU 94;TYR 168;GLU 231

References for Catalytic Mechanism
References	Sections	No. of steps in catalysis
[2]
[4]
[5]	p.115, Scheme1	2
[6]	Fig.3	4

References
[1]
Resource
Comments	crystallization, preliminary X-ray 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
[2]
Resource
Comments	catalytic amino acid residues
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
[3]
Resource
Comments	X-ray crystallography (2.3 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	1ghs
Related UniProtKB	P15737
[4]
Resource
Comments
Medline ID
PubMed ID	7729513
Journal	FEBS Lett
Year	1995
Volume	362
Pages	281-5
Authors	Jenkins J, Lo Leggio L, Harris G, Pickersgill R
Title	Beta-glucosidase, beta-galactosidase, family A cellulases, family F xylanases and two barley glycanases form a superfamily of enzymes with 8-fold beta/alpha architecture and with two conserved glutamates near the carboxy-terminal ends of beta-strands four and seven.
Related PDB
Related UniProtKB
[5]
Resource
Comments
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
[6]
Resource
Comments	structure-function relationships (review)
Medline ID
PubMed ID	11554481
Journal	Plant Mol Biol
Year	2001
Volume	47
Pages	73-91
Authors	Hrmova M, Fincher GB
Title	Structure-function relationships of beta-D-glucan endo- and exohydrolases from higher plants.
Related PDB
Related UniProtKB
[7]
Resource
Comments
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

Comments
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. Glu231 has been reported to be the nucleophilic residue of this enzyme (see [2]). In contrast, whilst the paper [2] indicated experimentally that Glu288 might be a general acid that protonates the glycosidic oxygen during hydrolysis, another paper [4] suggested that Glu94, which is conserved among family-1, 2, 5, 10 and 17, might play a role as the general acid. On the other hand, It is not clear which type of mechanisms is adopted by this enzyme, SN1 like mechanism or SN2-like reaction. The paper [5] suggested an SN2 mechanism, in which Glu231 serve as a nucleophile, attacking the anomeric carbon to generate a covalent-bonded intermediate. Moreover, whether this enzyme adopts a retention mechanism, or an inversion one, is still unknown [6]. However, considering the other family-17 enzyme, Lichenase (E.C. 3.2.1.72) (S00209 in EzCatDB), the mechanism must be similar to that. Furthermore, comparing the structural data with that of xylanase (E.C. 3.2.1.8) (D00479 in EzCatDB), Tyr168 might stabilize the leaving nucleophile, Glu231 in deglycosylation. On the other hand, Tyr168 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 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.
Glu231 has been reported to be the nucleophilic residue of this enzyme (see [2]). In contrast, whilst the paper [2] indicated experimentally that Glu288 might be a general acid that protonates the glycosidic oxygen during hydrolysis, another paper [4] suggested that Glu94, which is conserved among family-1, 2, 5, 10 and 17, might play a role as the general acid.
On the other hand, It is not clear which type of mechanisms is adopted by this enzyme, SN1 like mechanism or SN2-like reaction. The paper [5] suggested an SN2 mechanism, in which Glu231 serve as a nucleophile, attacking the anomeric carbon to generate a covalent-bonded intermediate.
Moreover, whether this enzyme adopts a retention mechanism, or an inversion one, is still unknown [6].
However, considering the other family-17 enzyme, Lichenase (E.C. 3.2.1.72) (S00209 in EzCatDB), the mechanism must be similar to that. Furthermore, comparing the structural data with that of xylanase (E.C. 3.2.1.8) (D00479 in EzCatDB), Tyr168 might stabilize the leaving nucleophile, Glu231 in deglycosylation. On the other hand, Tyr168 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	2009-02-26