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PDBsum entry 1byc
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Hydrolase(o-glycosyl)
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PDB id
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1byc
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References listed in PDB file
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Key reference
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Title
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Crystal structures of soybean beta-Amylase reacted with beta-Maltose and maltal: active site components and their apparent roles in catalysis.
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Authors
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B.Mikami,
M.Degano,
E.J.Hehre,
J.C.Sacchettini.
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Ref.
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Biochemistry, 1994,
33,
7779-7787.
[DOI no: ]
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PubMed id
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Abstract
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The crystal structures of catalytically competent soybean beta-amylase,
unliganded and bathed with small substrates (beta-maltose, maltal), were
determined at 1.9-2.2-A resolution. Two molecules of beta-maltose substrate bind
to the protein in tandem, with some maltotetraose enzymic condensation product
sharing the same binding sites. The beta-amylase soaked with maltal shows a
similar arrangement of two bound molecules of 2-deoxymaltose, the enzymic
hydration product. In each case the nonreducing ends of the saccharide ligands
are oriented toward the base of the protein's active site pocket. The catalytic
center, located between the bound disaccharides and found deeper in the pocket
than where the inhibitor alpha-cyclodextrin binds, is characterized by the
presence of oppositely disposed carboxyl groups of two conserved glutamic acid
residues. The OE2 carboxyl of Glu 186 is below the plane of the penultimate
glucose residue (Glc 2) of bound maltotetraose, 2.6 A from the oxygen atom of
that ligand's penultimate alpha-1,4-glucosidic linkage. The OE2 carboxyl of Glu
380 lies above the plane of Glc 2, 2.8 A from the O-1 atom of the more deeply
bound beta-maltose. Saccharide binding does not alter the spatial coordinates of
these two carboxyl groups or the overall conformation of the 57-kDa protein.
However, the saccharide complexes of the active enzyme are associated with a
significant (10 A) local conformational change in a peptide segment of a loop
(L3) that borders the active site pocket.(ABSTRACT TRUNCATED AT 250 WORDS)
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Secondary reference #1
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Title
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The 2.0-A resolution structure of soybean beta-Amylase complexed with alpha-Cyclodextrin.
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Authors
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B.Mikami,
E.J.Hehre,
M.Sato,
Y.Katsube,
M.Hirose,
Y.Morita,
J.C.Sacchettini.
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Ref.
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Biochemistry, 1993,
32,
6836-6845.
[DOI no: ]
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PubMed id
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