CAZypedia needs your help!
We have many unassigned pages in need of Authors and Responsible Curators. See a page that's out-of-date and just needs a touch-up? - You are also welcome to become a CAZypedian. Here's how.
Scientists at all career stages, including students, are welcome to contribute.
Learn more about CAZypedia's misson here and in this article.
Totally new to the CAZy classification? Read this first.

Glycoside Hydrolase Family 55

From CAZypedia
Jump to navigation Jump to search

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 Hydrolase family 55 consists exclusively of β-1,3-glucanases, including both exo- and endo-enzymes. All biochemically characterized members of this family are of fungal origin, although there are no yeast homologues. Several homologous genes have been identified in bacterial genomes, but none of their gene products are characterized.

The enzymes belonging to this family are generally called "laminarinases," because they hydrolyze laminarin from brown algae (β-1,3-glucan having single β-1,6-glucoside side chains: β-1,3/1,6-glucan). However, the physiological substrate for the enzymes might be fungal cell wall, whose major component is also β-1,3/1,6-glucan.

The majority of the members in this family are exo-glucan-1,3-β-glucosidases (EC3.2.1.58), which cleave the terminal β-1,3-glycosidic linkage at the non-reducing end of β-1,3-glucans or β-1,3/1,6-glucans. Many produce gentiobiose (β-D-glucopyranosyl-1,6-D-glucose) in addition to glucose during the degradation of β-1,3/1,6-glucan[1, 2].

Bgn13.1 from Trichoderma harzianum [3] and LamAI fromTrichoderma viride [4] were characterised as endo-acting enzymes (EC3.2.1.39).

Kinetics and Mechanism

Family 55 enzymes are inverting enzymes, 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-glucanases from fungi[6, 7], although the genes for these enzymes have not yet been described.

Catalytic Residues

The crystal structure of Lam55A from Phanerochaete chrysospoirum complexed with gluconolactone, suggests that Glu633 is the general acid. A candidate nucleophilic water was found near the C-1 atom of gluconolactone, but no acidic residue corresponding to the general base was identified in the vicinity of the water molecule.

In classical studies of a exo-β-1,3-glucanase from Basidiomycete QM-806, Jeffcoat and Kirkwood reported that chemical modification of histidine in the catalytic site of the enzyme caused irreversible loss of activity, suggesting a 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]. In this structure, two tandem β-helix domains are positioned side-by-side to form a rib cage-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]. See kinetics 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 | PubMed ID:8948426 [REF2]
  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 | PubMed ID:12594027 [REF3]
  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 | PubMed ID:7592488 [REF4]
  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 | PubMed ID:12843664 [REF5]
  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

    [REF6]
  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 PubMed ID:5416668 [REF7]
  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

    [REF8]
  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 PubMed ID:3100526 [REF9]
  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 | PubMed ID:19193645 [REF1]

All Medline abstracts: PubMed