Starch synthase

Short description: Enzyme family

starch synthase

Crystal structure of glycogen synthase 1 from Agrobacterium tumefaciens

Identifiers
EC number| 2.4.1.21
CAS number| 9030-10-8
Databases
IntEnz| IntEnz view
BRENDA| BRENDA entry
ExPASy| NiceZyme view
KEGG| KEGG entry
MetaCyc| metabolic pathway
PRIAM| profile
PDB structures| RCSB PDB PDBe PDBsum
Gene Ontology| AmiGO  / QuickGO
| Search

PMC| articles
PubMed| articles
NCBI| proteins

In enzymology, a starch synthase (EC 2.4.1.21) is an enzyme that catalyzes the chemical reaction

ADP-glucose + (1,4-alpha-D-glucosyl)n ⇌ ADP + (1,4-alpha-D-glucosyl)n+1

Thus, the two substrates of this enzyme are ADP-glucose and a chain of D-glucose residues joined by 1,4-alpha-glycosidic bonds, whereas its two products are ADP and an elongated chain of glucose residues. Plants use these enzymes in the biosynthesis of starch.

This enzyme belongs to the family of hexosyltransferases, specifically the glycosyltransferases. The systematic name of this enzyme class is ADP-glucose:1,4-alpha-D-glucan 4-alpha-D-glucosyltransferase. Other names in common use include ADP-glucose-starch glucosyltransferase, adenosine diphosphate glucose-starch glucosyltransferase, adenosine diphosphoglucose-starch glucosyltransferase, ADP-glucose starch synthase, ADP-glucose synthase, ADP-glucose transglucosylase, ADP-glucose-starch glucosyltransferase, ADPG starch synthetase, and ADPG-starch glucosyltransferase

Five isoforms seems to be present. GBSS which is linked to amylose synthesis. The others are SS1, SS2, SS3 and SS4. These have different roles in amylopectin synthesis. New work implies that SS4 is important for granule initiation. (Szydlowski et al., 2011)

## Structural studies

As of late 2007, 4 structures have been solved for this class of enzymes, with PDB accession codes 1RZU, 1RZV, 2BFW, and 2BIS.

## References

* "Biosynthesis of glucans in mung bean seedlings. Formation of beta-(1,4)-glucans from GDP-glucose and beta-(1,3)-glucans from UDP-glucose". Arch. Biochem. Biophys. 138 (2): 620-31. 1970. doi:10.1016/0003-9861(70)90389-9. PMID 4317490.
* "Studies on adenosine diphosphate d-glucose: α-1,4-glucan α-4-glucosyltransferase of sweet-corn endosperm". Biochim. Biophys. Acta 96 (2): 294-303. 1965. doi:10.1016/0926-6593(65)90013-5. PMID 14298833.
* Greenberg E; Preiss J (1965). "Biosynthesis of bacterial glycogen. II. Purification and properties of the adenosine diphosphoglucose:glycogen transglucosylase of arthrobacter species NRRL B1973". J. Biol. Chem. 240 (6): 2341-2348. doi:10.1016/S0021-9258(18)97328-X. PMID 14304835.
* "Starch and oligosaccharide synthesis from uridine diphosphate glucose". J. Biol. Chem. 236 (3): 636-641. 1961. doi:10.1016/S0021-9258(18)64280-2. PMID 13760681.
* Whelan, W.J. and Schultz, J. (Eds.), Miami Winter Symposia, vol. 1, North Holland, Utrecht, 1970, p. 122-138.

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Transferases: glycosyltransferases (EC 2.4)

2.4.1: Hexosyl-
transferases|

| Glucosyl-|

* Phosphorylase
* Starch
* Glycogen
* Myo-
* Glycogen synthase
* Debranching enzyme
* Branching enzyme
* 1,3-Beta-glucan synthase
* Ceramide glucosyltransferase
* N-glycosyltransferase

|

Galactosyl-|

* Lactose synthase
* B-N-acetylglucosaminyl-glycopeptide b-1,4-galactosyltransferase
* Glycoprotein-N-acetylgalactosamine 3-beta-galactosyltransferase (C1GALT1)

Glucuronosyl-|

* B3GAT1
* B3GAT2
* B3GAT3

* UGT1A1
* UGT1A3
* UGT1A4
* UGT1A5
* UGT1A6
* UGT1A7
* UGT1A8
* UGT1A9
* UGT1A10

* UGT2A1
* UGT2A2
* UGT2A3
* UGT2B4
* UGT2B7
* UGT2B10
* UGT2B11
* UGT2B15
* UGT2B17
* UGT2B28

* Hyaluronan synthase: HAS1
* HAS2
* HAS3

Fucosyl-|

* POFUT1
* POFUT2
* FUT1
* FUT2
* FUT3
* FUT4
* FUT5
* FUT6
* FUT7
* FUT8
* FUT9
* FUT10
* FUT11

Mannosyl-|

* Dolichyl-phosphate-mannose-protein mannosyltransferase
* POMT1
* POMT2
* DPM1
* DPM3

* ALG1
* ALG2
* ALG3
* ALG6
* ALG8
* ALG9
* ALG12

2.4.2: Pentosyl-
transferases|

| Ribose|

| ADP-ribosyltransferase|

* diphthamide ADP-ribosyltransferase
* Diphtheria toxin
* Pseudomonas exotoxin

* arginine ADP-ribosyltransferase
* Pertussis toxin
* Cholera toxin

* Poly ADP ribose polymerase

* Sirtuin

|

Phosphoribosyltransferase|

* Adenine phosphoribosyltransferase
* Hypoxanthine-guanine phosphoribosyltransferase
* Uracil phosphoribosyltransferase
* Amidophosphoribosyltransferase

Other|

* Purine nucleoside phosphorylase: Thymidine phosphorylase
* ECGF1

Other|

* Xylosyltransferase
* XYLT1
* XYLT2
* Arabinosyltransferase
* Indolylacetylinositol arabinosyltransferase

2.4.99: Sialyl
transferases|

* Beta-galactoside alpha-2,6-sialyltransferase
* Monosialoganglioside sialyltransferase
* ST8SIA4

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Enzymes

Activity|

* Active site
* Binding site
* Catalytic triad
* Oxyanion hole
* Enzyme promiscuity
* Catalytically perfect enzyme
* Coenzyme
* Cofactor
* Enzyme catalysis

Regulation|

* Allosteric regulation
* Cooperativity
* Enzyme inhibitor
* Enzyme activator

Classification|

* EC number
* Enzyme superfamily
* Enzyme family
* List of enzymes

Kinetics|

* Enzyme kinetics
* Eadie–Hofstee diagram
* Hanes–Woolf plot
* Lineweaver–Burk plot
* Michaelis–Menten kinetics

Types|

* EC1 Oxidoreductases (list)
* EC2 Transferases (list)
* EC3 Hydrolases (list)
* EC4 Lyases (list)
* EC5 Isomerases (list)
* EC6 Ligases (list)
* EC7 Translocases (list)

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