Cofactors

There are no Cofactors for this Enzyme

Reaction Mechanism

4-alpha-glucanotransferase By Reference

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
View Reaction Mechanisms in M-CSA

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

  View all in Brenda

Associated Proteins

Citations

• Photometric assay of maltose and maltose-forming enzyme activity by using 4-alpha-glucanotransferase (DPE2) from higher plants.
• Mycobacterium leprae specific genomic target in the promoter region of probable 4-alpha-glucanotransferase (ML1545) gene with potential sensitivity for polymerase chain reaction based diagnosis of leprosy.
• Exploring the roles of amylopectin in starch modification with Limosilactobacillus reuteri 121 4,6-α-glucanotransferase via developed methods.
• Structural characterization of potato starch modified by a 4,6-α-glucanotransferase B from Lactobacillus reuteri E81.
• Differentiated digestion resistance and physicochemical properties of linear and α-1,2/α-1,3 branched isomaltodextrins prepared by 4,6-α-glucanotransferase and branching sucrases.
• The Role of a Loop in the Non-catalytic Domain B on the Hydrolysis/Transglycosylation Specificity of the 4-α-Glucanotransferase from Thermotoga maritima.
• Cost-effective and controllable synthesis of isomalto/malto-polysaccharides from β-cyclodextrin by combined action of cyclodextrinase and 4,6-α-glucanotransferase GtfB.
• CRYOPROTECTANT COMPRISING STARCH TREATED BY 4-[alpha]-GLUCANOTRANSFERASE
• Enzymatic potato starch modification and structure-function analysis of six diverse GH77 4-alpha-glucanotransferases.
• Multiple approaches of loop region modification for thermostability improvement of 4,6-α-glucanotransferase from Limosilactobacillus fermentum NCC 3057.
• Hemin availability induces coordinated DNA methylation and gene expression changes in Porphyromonas gingivalis.