2-pyrone-4,6-dicarboxylate lactonase

In enzymology, 2-pyrone-4,6-dicarboxylate lactonase (EC 3.1.1.57) is an enzyme that catalyzes the reversible hydrolytic chemical reaction

2-pyrone-4,6-dicarboxylate + H2O 4-carboxy-2-hydroxyhexa-2,4-dienedioate and 4-oxalomesaconate
2-pyrone-4,6-dicarboxylate lactonase (LigI)
Identifiers
EC number3.1.1.57
CAS number84177-55-9
Databases
IntEnzIntEnz view
BRENDABRENDA entry
ExPASyNiceZyme view
KEGGKEGG entry
MetaCycmetabolic pathway
PRIAMprofile
PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / QuickGO

Thus, the two substrates of this enzyme are 2-pyrone-4,6-dicarboxylate[1] and H2O, whereas its product is a tautomeric mixture of 4-oxalomesaconate[2] and 4-carboxy-2-hydroxymuconate.[3]

This enzyme belongs to the Amidohydrolase superfamily of enzymes and is a member of Cluster of Orthologous Groups (COG) 3618. The systematic name of this enzyme is 2-pyrone-4,6-dicarboxylate lactonase but is also known as LigI. This enzyme is found to play an important role in the metabolism of lignin-derived aromatic compounds in both the syringate degradation pathway[4] and the protocatechuate 4,5-cleavage pathway.[5]

LigI from Sphingomonas is of particular interest as it has been shown to be the first member of the amidohydrolase superfamily to not require a divalent metal cation for catalytic activity.[6]

Mechanism

The mechanism of catalysis of LigI has been determined by crystallography and NMR analysis. More specifically, the hydrolytic water molecule is activated by the transfer of a proton to Asp-248 whereas the carbonyl group of the 2-pyrone-4,6-dicarboxylate (PDC) lactone substrate is activated by hydrogen bonding interactions with His-180, His-31, and His-33.[6]

References
  1. "2-pyrone-4,6-dicarboxylate". MetaCyc. SRI International.
  2. "(1E)-4-oxobut-1-ene-1,2,4-tricarboxylate". MetaCyc. SRI International.
  3. "(1Z,3Z)-4-hydroxybuta-1,3-diene-1,2,4-tricarboxylate". MetaCyc. SRI International.
  4. "syringate degradation". MetaCyc. SRI International.
  5. "protocatechuate degradation I (meta-cleavage pathway)". MetaCyc. SRI International.
  6. Hobbs ME, Malashkevich V, Williams HJ, Xu C, Sauder JM, Burley SK, Almo SC, Raushel FM (April 2012). "Structure and Catalytic Mechanism of LigI: Insight into the Amidohydrolase Enzymes of cog3618 and Lignin Degradation". Biochemistry. 51 (16): 3497–507. doi:10.1021/bi300307b. PMC 3416963. PMID 22475079.

Further reading


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