PDBsum entry 1byc

Hydrolase(o-glycosyl)

PDB id: 1byc

Contents

Protein chain

491 a.a. *

Ligands

BGC-GLC-GLC-GLC

SO4

Waters ×332

* Residue conservation analysis

PDB id:

1byc

Name:

Hydrolase(o-glycosyl)

Title:

Crystal structures of soybean beta-amylase reacted with beta-maltose and maltal: active site components and their apparent role in catalysis

Structure:

Beta-amylase. Chain: a. Engineered: yes

Source:

Glycine max. Soybean. Organism_taxid: 3847

Resolution:

2.20Å R-factor: 0.149

Authors:

B.Mikami,M.Degano,E.J.Hehre,J.C.Sacchettini

Key ref:

B.Mikami et al. (1994). Crystal structures of soybean beta-amylase reacted with beta-maltose and maltal: active site components and their apparent roles in catalysis. Biochemistry, 33, 7779-7787. PubMed id: 8011643 DOI: 10.1021/bi00191a005

Date:

25-Jan-94 Release date: 31-Jul-94

Protein chain

P10538  (AMYB_SOYBN) -  Beta-amylase from Glycine max

Seq: 496 a.a.

Struc: 491 a.a.

Enzyme reactions

• Enzyme class: E.C.3.2.1.2 - beta-amylase.
• Reaction: Hydrolysis of 1,4-alpha-glucosidic linkages in polysaccharides so as to remove successive maltose units from the non-reducing ends of the chains.

DOI no: 10.1021/bi00191a005

Biochemistry 33:7779-7787 (1994)

PubMed id: 8011643

Crystal structures of soybean beta-amylase reacted with beta-maltose and maltal: active site components and their apparent roles in catalysis.

B.Mikami, M.Degano, E.J.Hehre, J.C.Sacchettini.

ABSTRACT

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)