TY - JOUR
T1 - The apo structure of sucrose hydrolase from Xanthomonas campestris pv. campestris shows an open active-site groove
AU - Champion, Elise
AU - Remaud-Simeon, Magali
AU - Skov, Lars Kobberøe
AU - Kastrup, Jette Sandholm
AU - Gajhede, Michael
AU - Mirza, Osman Asghar
N1 - Keywords: Biocatalysis; Catalytic Domain; Crystallography, X-Ray; Glycoside Hydrolases; Models, Molecular; Protein Structure, Tertiary; Sucrose; Xanthomonas campestris
PY - 2009
Y1 - 2009
N2 - Glycoside 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.
AB - Glycoside 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.
KW - Former Faculty of Pharmaceutical Sciences
U2 - 10.1107/S0907444909040311
DO - 10.1107/S0907444909040311
M3 - Journal article
C2 - 19966417
SN - 0907-4449
VL - 65
SP - 1309
EP - 1314
JO - Acta Crystallographica. Section D: Biological Crystallography
JF - Acta Crystallographica. Section D: Biological Crystallography
IS - 12
ER -