1-aminocyclopropane-1-carboxylate synthase
Catalyzes the formation of 1-aminocyclopropane-1-carboxylate, a direct precursor of ethylene in higher plants
Reference Protein and Structure
- Sequence
-
P37821
(1.4.-.-, 4.4.1.14)
(Sequence Homologues)
(PDB Homologues)
- Biological species
-
Malus domestica (apple)
- PDB
-
1b8g
- 1-AMINOCYCLOPROPANE-1-CARBOXYLATE SYNTHASE
(2.37 Å)
- Catalytic CATH Domains
-
3.40.640.10
(see all for 1b8g)
- Cofactors
- Pyridoxal 5'-phosphate(2-) (1)
Enzyme Reaction (EC:4.4.1.14)
→
+
+
Alternative enzyme names: 1-aminocyclopropane-1-carboxylate synthetase, 1-aminocyclopropane-1-carboxylic acid synthase, 1-aminocyclopropanecarboxylate synthase, ACC synthase, Aminocyclopropanecarboxylate synthase, Aminocyclopropanecarboxylic acid synthase, S-adenosyl-L-methionine methylthioadenosine-lyase,
Enzyme Mechanism
Introduction
The S-adenosyl-L-methionine substrate undergoes a transaldimination reaction with the Lysine bound PLP, resulting in the aldimine intermediate. The S-methyl-5'-thioadenosine is eliminated with concomitant cyclisation of the bound amino acid intermediate. The second transaldimination reaction between Lys and PLP results in the elimination of the cyclic product and regeneration of the enzyme's active site.
Catalytic Residues Roles
| UniProt | PDB* (1b8g) | ||
| Lys273 | Lys273(271)A | Acts as a general acid base and as a catalytic nucleophile. Starts (and ends) the reaction covalently bound to the PLP cofactor. | covalent catalysis, proton shuttle (general acid/base) |
| Ile232, Tyr145 | Ile232(230)A, Tyr145(143)A | Sandwiches the pyridine ring, holding it in the correct position. | steric role |
| Asp230 | Asp230(228)A | Forms a hydrogen bond with the pyridine nitrogen, stabilising the intermediates. | electrostatic stabiliser |
*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
References
- Jakubowicz M (2002), Acta Biochim Pol, 49, 757-774. Structure, catalytic activity and evolutionary relationships of 1-aminocyclopropane-1-carboxylate synthase, the key enzyme of ethylene synthesis in higher plants. DOI:024903757. PMID:12422245.
- Capitani G et al. (1999), J Mol Biol, 294, 745-756. Structure of 1-aminocyclopropane-1-carboxylate synthase, a key enzyme in the biosynthesis of the plant hormone ethylene. DOI:10.1006/jmbi.1999.3255. PMID:10610793.
Catalytic Residues Roles
| Residue | Roles |
|---|---|
| Lys273(271)A | covalent catalysis, proton shuttle (general acid/base) |
| Tyr145(143)A | activator, steric role |
| Ile232(230)A | steric role |
| Asp230(228)A | electrostatic stabiliser |