2wpg | pdb_00002wpg
Sucrose Hydrolase
Structural highlights
Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedGlycoside hydrolase family 13 (GH-13) mainly contains starch-degrading or starch-modifying enzymes. Sucrose hydrolases utilize sucrose instead of amylose as the primary glucosyl donor. Here, the catalytic properties and X-ray structure of sucrose hydrolase from Xanthomonas campestris pv. campestris are reported. Sucrose hydrolysis catalyzed by the enzyme follows Michaelis-Menten kinetics, with a K(m) of 60.7 mM and a k(cat) of 21.7 s(-1). The structure of the enzyme was solved at a resolution of 1.9 A in the resting state with an empty active site. This represents the first apo structure from subfamily 4 of GH-13. Comparisons with structures of the highly similar sucrose hydrolase from X. axonopodis pv. glycines most notably showed that residues Arg516 and Asp138, which form a salt bridge in the X. axonopodis sucrose complex and define part of the subsite -1 glucosyl-binding determinants, are not engaged in salt-bridge formation in the resting X. campestris enzyme. In the absence of the salt bridge an opening is created which gives access to subsite -1 from the ;nonreducing' end. Binding of the glucosyl moiety in subsite -1 is therefore likely to induce changes in the conformation of the active-site cleft of the X. campestris enzyme. These changes lead to salt-bridge formation that shortens the groove. Additionally, this finding has implications for understanding the molecular mechanism of the closely related subfamily 4 glucosyl transferase amylosucrase, as it indicates that sucrose could enter the active site from the ;nonreducing' end during the glucan-elongation cycle. The apo structure of sucrose hydrolase from Xanthomonas campestris pv. campestris shows an open active-site groove.,Champion E, Remaud-Simeon M, Skov LK, Kastrup JS, Gajhede M, Mirza O Acta Crystallogr D Biol Crystallogr. 2009 Dec;65(Pt 12):1309-14. Epub 2009 Nov, 17. PMID:19966417[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
Contents | ||||||||||||||||
