Glycoside Hydrolase Family 55

* Authors: Takuya Ishida and ^^^Kiyohiko Igarashi^^^

• Responsible Curator: ^^^User:ShinyaFushinobu|Shinya Fushinobu^^^

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Glycoside Hydrolase Family 55
Clan	none
Mechanism	inverting
Active site residues	not known
CAZy DB link
http://www.cazy.org/fam/GH55.html

Substrate specificities

Glycoside Hydrolases of family 55 exclusively consists of β-1,3-glucanases, including both exo- and endo-enzymes, at this moment. All of biochemically characterized members of this family have fungal origin, but not from yeast. Several homologous genes are found from Bacterial genomes, but none of their gene products are characterized.

The enzymes belonging to this family are generally called "laminarinase" because the enzyme hydrolyzes laminarin "β-1,3-glucan having single β-1,6-glucosides: β-1,3/1,6-glucan) from brown algae. But the physiological substrate for the enzymes might be fungal cell wall, whose major component is also β-1,3/1,6-glucan.

Since the majority of the members in this family produce glucose from β-1,3-glucan, they should be categorized as a glucan-1,3-β-glucosidase (EC3.2.1.58). Exo-β-1,3-glucanases in this family cleave the terminal β-1,3-glycosidic linkage at non-reducing end of %beta;-1,3-glucans or %beta;-1,3/1,6-glucans. Many of them produces gentiobiose (&beta-D-glucopyranosyl-1,6-D-glucose) in addition to glucose during degradation of b-1,3/1,6-glucan[1][2].

Bgn13.1 from Trichoderma harzianum [3] and LamAI fromTrichoderma viride [4] were described as endo-type enzymes (EC3.2.1.39) based on the experimental results.

Kinetics and Mechanism

Family 55 enzymes are inverting enzyme, as shown by NMR analysis on ExgS from Aspergillus saitoi [5]. This result is consistent with many classical reports on gentiobiose-producing exo-β-1,3-glucanase from fungi[6][7], but the genes for these enzymes have not cloned yet.

Catalytic Residues

From the crystal structure of Lam55A from Phanerochaete chrysospoirum complexed with gluconolactone, Glu633 appears to be the general acid. A possible nucleophilic water was found near the C-1 atom of gluconolactone, but no acidic residue that can be the general base was found around the water.

In the classical studies for exo-β-1,3-glucanase from Basidiomycete QM-806, Jeffcoat and Kirkwood reported the chemical modification of histidine in the catalytic site of the enzyme caused irreversible loss of the activity, suggesting crucial role of the histidine residues [8].

Three-dimensional structures

The first solved 3-D structure was exo-β-1,3-glucanase Lam55A from P. chrysosporium [9]. Two tandem &beta-helix domains are positioned side by side to form a rib-like structure. The active site is located between the two β-helix domains.

Family Firsts

First sterochemistry determination

Probably ExgS from A. saitoi by ¹H-NMR analysis [5]. Seekinetics and mechanism.

First gene cloning

BGN13.1 from T. harzianum. [6].

First general acid residue identification

First general base residue identification

First 3-D structure

Lam55A from Phanerochaete chrysosporium K-3 by X-ray crystallography (PDB 3eqo) [9].

References

1. Pitson SM, Seviour RJ, McDougall BM, Woodward JR, and Stone BA. (1995). Purification and characterization of three extracellular (1-->3)-beta-D-glucan glucohydrolases from the filamentous fungus Acremonium persicinum. Biochem J. 1995;308 ( Pt 3)(Pt 3):733-41. DOI:10.1042/bj3080733 |
2. Bara MT, Lima AL, and Ulhoa CJ. (2003). Purification and characterization of an exo-beta-1,3-glucanase produced by Trichoderma asperellum. FEMS Microbiol Lett. 2003;219(1):81-5. DOI:10.1016/S0378-1097(02)01191-6 |
3. de la Cruz J, Pintor-Toro JA, Benítez T, Llobell A, and Romero LC. (1995). A novel endo-beta-1,3-glucanase, BGN13.1, involved in the mycoparasitism of Trichoderma harzianum. J Bacteriol. 1995;177(23):6937-45. DOI:10.1128/jb.177.23.6937-6945.1995 |
4. Nobe R, Sakakibara Y, Fukuda N, Yoshida N, Ogawa K, and Suiko M. (2003). Purification and characterization of laminaran hydrolases from Trichoderma viride. Biosci Biotechnol Biochem. 2003;67(6):1349-57. DOI:10.1271/bbb.67.1349 |

5. Kasahara S, Nakajima T, Miyamoto C, Wada K, Furuichi Y, and Ichishima E. Characterization and mode of action of exo-1,3-β-D-glucanase from Aspergillus saitoi. J Ferment Bioeng 74 (4), 238-240 (1992).DOI:10.1016/0922-338X(92)90118-E

6. Nelson TE (1970). The hydrolytic mechanism of an exo-beta-(1--3)-D-glucanase. J Biol Chem. 1970;245(4):869-72. | Google Books | Open Library

7. Nagasaki N, Saito K, and Yarnamoto S. Purification and characterization of an exo-β-l,3-glucanase from a fungi imperfecti. Agric Biol Cbem 41, 493-502 (1977).JOI:JST.Journalarchive/bbb1961/41.493

8. Jeffcoat R and Kirkwood S. (1987). Implication of histidine at the active site of exo-beta-(1-3)-D-glucanase from Basidiomycete sp. QM 806. J Biol Chem. 1987;262(3):1088-91. | Google Books | Open Library
9. Ishida T, Fushinobu S, Kawai R, Kitaoka M, Igarashi K, and Samejima M. (2009). Crystal structure of glycoside hydrolase family 55 {beta}-1,3-glucanase from the basidiomycete Phanerochaete chrysosporium. J Biol Chem. 2009;284(15):10100-9. DOI:10.1074/jbc.M808122200 |