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In enzymology, 2-pyrone-4,6-dicarboxylate lactonase () 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 Thus, the two substrates of this enzyme are 2-pyrone-4,6-dicarboxylate and H2O, whereas its product is a tautomeric mixture of 4-oxalomesaconate and 4-carboxy-2-hydroxymuconate. 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 and the protocatechuate 4,5-cleavage pathway. 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.〔 == 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「2-pyrone-4,6-dicarboxylate lactonase」の詳細全文を読む スポンサード リンク
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