Glycoside hydrolase family 14

Glycosyl hydrolase family 14

beta-amylase from bacillus cereus var. mycoides in complex with maltose
Identifiers
Symbol Glyco_hydro_14
Pfam PF01373
Pfam clan CL0058
InterPro IPR001554
SCOP 1byb
SUPERFAMILY 1byb
CAZy GH14

In molecular biology, Glycoside hydrolase family 14 is a family of glycoside hydrolases.

Glycoside hydrolases EC 3.2.1. are a widespread group of enzymes that hydrolyse the glycosidic bond between two or more carbohydrates, or between a carbohydrate and a non-carbohydrate moiety. A classification system for glycoside hydrolases, based on sequence similarity, has led to the definition of >100 different families.[1][2][3] This classification is available on the CAZy(http://www.cazy.org/GH1.html) web site,[4] and also discussed at CAZypedia, an online encyclopedia of carbohydrate active enzymes.[5]

Glycoside hydrolase family 14 CAZY GH_14 comprises enzymes with only one known activity; beta-amylase (EC 3.2.1.2). A Glu residue has been proposed as a catalytic residue, but it is not known if it is the nucleophile or the proton donor. Beta-amylase[6][7] is an enzyme that hydrolyzes 1,4-alpha-glucosidic linkages in starch-type polysaccharide substrates so as to remove successive maltose units from the non-reducing ends of the chains. Beta-amylase is present in certain bacteria as well as in plants.

Three highly conserved sequence regions are found in all known beta-amylases. The first of these regions is located in the N-terminal section of the enzymes and contains an aspartate which is known[8] to be involved in the catalytic mechanism. The second, located in a more central location, is centred on a glutamate which is also involved[9] in the catalytic mechanism.

The 3D structure of a complex of soybean beta-amylase with an inhibitor (alpha-cyclodextrin) has been determined to 3.0A resolution by X-ray diffraction.[10] The enzyme folds into large and small domains: the large domain has a (beta alpha)8 super-secondary structural core, while the smaller is formed from two long loops extending from the beta-3 and beta-4 strands of the (beta alpha)8 fold.[10] The interface of the two domains, together with shorter loops from the (beta alpha)8 core, form a deep cleft, in which the inhibitor binds.[10] Two maltose molecules also bind in the cleft, one sharing a binding site with alpha-cyclodextrin, and the other sitting more deeply in the cleft.[10]

References

  1. ↑ Henrissat B, Callebaut I, Mornon JP, Fabrega S, Lehn P, Davies G (1995). "Conserved catalytic machinery and the prediction of a common fold for several families of glycosyl hydrolases". Proc. Natl. Acad. Sci. U.S.A. 92 (15): 7090–7094. doi:10.1073/pnas.92.15.7090. PMC 41477. PMID 7624375.
  2. ↑ Henrissat B, Davies G (1995). "Structures and mechanisms of glycosyl hydrolases". Structure 3 (9): 853–859. doi:10.1016/S0969-2126(01)00220-9. PMID 8535779.
  3. ↑ Bairoch, A. "Classification of glycosyl hydrolase families and index of glycosyl hydrolase entries in SWISS-PROT". 1999.
  4. ↑ Henrissat, B. and Coutinho P.M. "Carbohydrate-Active Enzymes server". 1999.
  5. ↑ CAZypedia, an online encyclopedia of carbohydrate-active enzymes.
  6. ↑ Fukazawa C, Mikami B, Morita Y (1988). "Primary structure and function of beta-amylase". Seikagaku 60 (3): 211–216. PMID 2457058.
  7. ↑ Friedberg F, Rhodes C (1988). "Segments of amino acid sequence similarity in beta-amylases". Protein Seq. Data Anal. 1 (6): 499–501. PMID 2464171.
  8. ↑ Sakiyama F, Nitta Y, Isoda Y, Toda H (1989). "Identification of glutamic acid 186 affinity-labeled by 2,3-epoxypropyl alpha-D-glucopyranoside in soybean beta-amylase". J. Biochem. 105 (4): 573–576. PMID 2474529.
  9. ↑ Totsuka A, Nong VH, Kadokawa H, Itoh Y, Fukazawa C, Kim CS (1994). "Residues essential for catalytic activity of soybean beta-amylase". Eur. J. Biochem. 221 (2): 649–654. doi:10.1111/j.1432-1033.1994.tb18777.x. PMID 8174545.
  10. 1 2 3 4 Katsube Y, Mikami B, Sato M, Shibata T, Hirose M, Aibara S, Morita Y (1992). "Three-dimensional structure of soybean beta-amylase determined at 3.0 A resolution: preliminary chain tracing of the complex with alpha-cyclodextrin". J. Biochem. 112 (4): 541–546. PMID 1491009.

This article incorporates text from the public domain Pfam and InterPro IPR001554

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