Maltose phosphorylase

 

Maltose phosphorylase (MP) catalyses the conversion of maltose and inorganic phosphate into beta-D-glucose-1-phosphate and glucose without a cofactor. It belongs to family 65 of glycoside hydrolases and can be classed as an inverting phosphorylase for the inversion of the anomeric configuration. The reverse reaction of maltose phosphorylase is of particular interest to synthesise low cost disaccharides for large scale oligosaccharide production.

 

Reference Protein and Structure

Sequence
Q7SIE1 UniProt IPR017045 (Sequence Homologues) (PDB Homologues)
Biological species
Lactobacillus brevis (Bacteria) Uniprot
PDB
1h54 - Maltose phosphorylase from Lactobacillus brevis (2.15 Å) PDBe PDBsum 1h54
Catalytic CATH Domains
1.50.10.10 CATHdb (see all for 1h54)
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Enzyme Reaction (EC:2.4.1.8)

maltose
CHEBI:17306ChEBI
+
hydrogenphosphate
CHEBI:43474ChEBI
→
D-glucopyranose
CHEBI:4167ChEBI
+
beta-D-glucose 1-phosphate(2-)
CHEBI:57684ChEBI

Enzyme Mechanism

Introduction

By analogy to the catalytic domain of glucoamylase, Glu487 of MP acts as an acid to protonate the glycosidic bond oxygen and one of the phosphate oxygen performs a nucleophilic attack at the C1 anomeric carbon of the substrate to yield glucose-1-phosphate and glucose. As this reaction is reversible, reprotonation of Glu487 can occur in the reverse phospholysis mechanism.

Catalytic Residues Roles

UniProt PDB* (1h54)
Glu487 Glu487A It acts as an acid to protonate the glycosidic bond. proton donor
*PDB label guide - RESx(y)B(C) - RES: Residue Name; x: Residue ID in PDB file; y: Residue ID in PDB sequence if different from PDB file; B: PDB Chain; C: Biological Assembly Chain if different from PDB. If label is "Not Found" it means this residue is not found in the reference PDB.

Chemical Components

bimolecular nucleophilic substitution, proton transfer, overall reactant used, overall product formed

References

  1. Nakai H et al. (2010), Carbohydr Res, 345, 1061-1064. Efficient one-pot enzymatic synthesis of alpha-(1-->4)-glucosidic disaccharides through a coupled reaction catalysed by Lactobacillus acidophilus NCFM maltose phosphorylase. DOI:10.1016/j.carres.2010.03.021. PMID:20392438.
  2. Vuong TV et al. (2010), Biotechnol Bioeng, 107, 195-205. Glycoside hydrolases: Catalytic base/nucleophile diversity. DOI:10.1002/bit.22838. PMID:20552664.
  3. Luley-Goedl C et al. (2010), Biotechnol J, 5, 1324-1338. Carbohydrate synthesis by disaccharide phosphorylases: reactions, catalytic mechanisms and application in the glycosciences. DOI:10.1002/biot.201000217. PMID:21154671.
  4. Egloff MP et al. (2001), Structure, 9, 689-697. Crystal structure of maltose phosphorylase from Lactobacillus brevis: unexpected evolutionary relationship with glucoamylases. PMID:11587643.

Step 1. Nucleophilic attack by the incoming phosphate group. Glu487 protonates the glycosidic oxygen to enhance it's leaving group ability.

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Catalytic Residues Roles

Residue Roles
Glu487A proton donor

Chemical Components

ingold: bimolecular nucleophilic substitution, proton transfer, overall reactant used, overall product formed
Download: Image, Marvin File

Step 1. Nucleophilic attack by the incoming phosphate group. Glu487 protonates the glycosidic oxygen to enhance it's leaving group ability.

Products.

Contributors

Mei Leung, Gemma L. Holliday, Morwenna Hall