Glycoside hydrolase family 14 explained

Symbol:Glyco_hydro_14
Glycosyl hydrolase family 14
Pfam:PF01373
Pfam Clan:CL0058
Interpro:IPR001554
Scop:1byb
Cazy:GH14

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

Glycoside hydrolases 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 web site,[4] [5] and also discussed at CAZypedia, an online encyclopedia of carbohydrate active enzymes.[6] [7]

Glycoside hydrolase family 14 CAZY GH_14 comprises enzymes with only one known activity; beta-amylase . 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[8] [9] 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[10] to be involved in the catalytic mechanism. The second, located in a more central location, is centred on a glutamate which is also involved[11] 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.[12] 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. 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.[12] 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.

Notes and References

  1. Henrissat B, Callebaut I, Fabrega S, Lehn P, Mornon JP, Davies G . Conserved catalytic machinery and the prediction of a common fold for several families of glycosyl hydrolases . Proceedings of the National Academy of Sciences of the United States of America . 92 . 15 . 7090–4 . July 1995 . 7624375 . 41477 . 10.1073/pnas.92.15.7090 . 1995PNAS...92.7090H . free .
  2. Davies G, Henrissat B . Structures and mechanisms of glycosyl hydrolases . Structure . 3 . 9 . 853–9 . September 1995 . 8535779 . 10.1016/S0969-2126(01)00220-9 . free .
  3. Henrissat B, Bairoch A . Updating the sequence-based classification of glycosyl hydrolases . The Biochemical Journal . 316 . Pt 2 . 695–6 . June 1996 . 8687420 . 1217404 . 10.1042/bj3160695.
  4. Web site: Home. CAZy.org. en. 2018-03-06.
  5. Lombard V, Golaconda Ramulu H, Drula E, Coutinho PM, Henrissat B . The carbohydrate-active enzymes database (CAZy) in 2013 . Nucleic Acids Research . 42 . Database issue . D490-5 . January 2014 . 24270786 . 3965031 . 10.1093/nar/gkt1178 .
  6. Web site: Glycoside Hydrolase Family 14. CAZypedia.org. en. 2018-03-06.
  7. Ten years of CAZypedia: a living encyclopedia of carbohydrate-active enzymes . Glycobiology . 28 . 1 . 3–8 . December 2018 . 29040563 . 10.1093/glycob/cwx089 . CAZypedia Consortium . free .
  8. Mikami B, Morita Y, Fukazawa C . [Primary structure and function of beta-amylase] . Seikagaku. The Journal of Japanese Biochemical Society . 60 . 3 . 211–6 . March 1988 . 2457058 .
  9. Friedberg F, Rhodes C . Segments of amino acid sequence similarity in beta-amylases . Protein Sequences & Data Analysis . 1 . 6 . 499–501 . 1988 . 2464171 .
  10. Nitta Y, Isoda Y, Toda H, Sakiyama F . Identification of glutamic acid 186 affinity-labeled by 2,3-epoxypropyl alpha-D-glucopyranoside in soybean beta-amylase . Journal of Biochemistry . 105 . 4 . 573–6 . April 1989 . 2474529 . 10.1093/oxfordjournals.jbchem.a122706 .
  11. Totsuka A, Nong VH, Kadokawa H, Kim CS, Itoh Y, Fukazawa C . Residues essential for catalytic activity of soybean beta-amylase . European Journal of Biochemistry . 221 . 2 . 649–54 . April 1994 . 8174545 . 10.1111/j.1432-1033.1994.tb18777.x .
  12. Mikami B, Sato M, Shibata T, Hirose M, Aibara S, Katsube Y, Morita Y . Three-dimensional structure of soybean beta-amylase determined at 3.0 A resolution: preliminary chain tracing of the complex with alpha-cyclodextrin . Journal of Biochemistry . 112 . 4 . 541–6 . October 1992 . 1491009 . 10.1093/oxfordjournals.jbchem.a123935 .

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