Enzyme - 4-alpha-glucanotransferase

Alternative Name(s)
  • Dextrin glycosyltransferase.
  • Oligo-1,4-1,4-glucantransferase.
  • D-enzyme.
  • Disproportionating enzyme.

Catalytic Activity

Transfers a segment of a (1->4)-alpha-D-glucan to a new position in an acceptor, which may be glucose or a (1->4)-alpha-D-glucan.


There are no Cofactors for this Enzyme

Reaction Mechanism

    Amylomaltase enzymes are structurally and mechanistically related to alpha amylases, although they almost exclusively catalyse trans-glycosylation reactions whereas alpha amylase enzymes catalyse hydrolysis reactions. The amylomaltase enzyme catalyses amylose disproportionation and the synthesis of large cyclic glucans, making these enzymes of interest to chemical and pharmaceutical industries.

    Three conserved carboxylic acid residues are central to the catalytic mechanism. The first acid residue acts as a general acid towards the oxygen of the scissile glycosidic bond. Simultaneously, the oxygen of a second carboxylic residue acts as a nucleophile towards the C1 of the substrate. This forms a covalent glycosyl-enzyme intermediate though a planar oxocarbenium intermediate. This covalent intermediate can be broken down by either a water molecule, resulting in hydrolysis or by a hydroxyl group of another sugar molecule. The third catalytic carboxylic residue binds the sugar in the -1 subsite, distorting it towards a partially planar conformation and contributing to the transition state stabilisation through hydrogen bonding.
    Catalytic Residues
    AA Uniprot Uniprot Resid PDB PDB Resid
    Asp O87172 293 1cwy 293
    Glu O87172 340 1cwy 340
    Asp O87172 395 1cwy 395

Reaction Parameters

  • Kinetic Parameters
    Organism KM Value [mM] Substrate Comment
    Thermus brockianus 0.00035 maltotriose mutant F251G, pH 6.0, 70°C
    Corynebacterium glutamicum 0.0017 maltopentaose mutant enzyme N287Y, at pH 6.0 and 30°C
    Manihot esculenta 12.9 maltotriose at pH 7.0 and 37 °C
    Arabidopsis thaliana 21.6 maltotriose at pH 7.0 and 37 °C
  • Temperature
    Organism Temperature Range Comment
    Escherichia coli 30 - 55
    Thermotoga maritima 30 - 90
    Thermus thermophilus 50 - 90
    Thermococcus litoralis 50 - 100
    Aquifex aeolicus 60 - 100 60°C: about 50% of maximal activity, 100°C: about 30% of maximal activity
  • pH
    Organism pH Range Comment
    Thermotoga maritima 3.5 - 10
    Bacillus sp. (in: Bacteria) 4 - 6
    Escherichia coli 4 - 9
    Thermus thermophilus 4 - 7.5 pH dependence of wild-type and mutant enzymes, D293N and E340Q are active below pH 6.5 and pH 5.5, respectively, but precipitate during the necessary prolonged incubation times, wild-type Tt AMase precipitates below pH 5.5 under similar extended incubation times as well, overview
    Aspergillus niger 4.2 - 8

Associated Proteins

Protein name Organism
4-alpha-glucanotransferase DPE1, chloroplastic/amyloplastic Mouse-ear cress
4-alpha-glucanotransferase DPE2 Mouse-ear cress
4-alpha-glucanotransferase Thermococcus litoralis (strain ATCC 51850 / DSM 5473 / JCM 8560 / NS-C)
4-alpha-glucanotransferase, chloroplastic/amyloplastic Potato
Glycoside hydrolase, family 77 Beggiatoa sp. PS