2nxw
From Proteopedia
| Line 4: | Line 4: | ||
==Overview== | ==Overview== | ||
| - | Phenylpyruvate decarboxylase (PPDC) of Azospirillum brasilense, involved | + | Phenylpyruvate decarboxylase (PPDC) of Azospirillum brasilense, involved in the biosynthesis of the plant hormone indole-3-acetic acid and the antimicrobial compound phenylacetic acid, is a thiamine diphosphate-dependent enzyme that catalyses the nonoxidative decarboxylation of indole- and phenylpyruvate. Analogous to yeast pyruvate decarboxylases, PPDC is subject to allosteric substrate activation, showing sigmoidal v versus [S] plots. The present paper reports the crystal structure of this enzyme determined at 1.5 A resolution. The subunit architecture of PPDC is characteristic for other members of the pyruvate oxidase family, with each subunit consisting of three domains with an open alpha/beta topology. An active site loop, bearing the catalytic residues His112 and His113, could not be modelled due to flexibility. The biological tetramer is best described as an asymmetric dimer of dimers. A cysteine residue that has been suggested as the site for regulatory substrate binding in yeast pyruvate decarboxylase is not conserved, requiring a different mechanism for allosteric substrate activation in PPDC. Only minor changes occur in the interactions with the cofactors, thiamine diphosphate and Mg2+, compared to pyruvate decarboxylase. A greater diversity is observed in the substrate binding pocket accounting for the difference in substrate specificity. Moreover, a catalytically important glutamate residue conserved in nearly all decarboxylases is replaced by a leucine in PPDC. The consequences of these differences in terms of the catalytic and regulatory mechanism of PPDC are discussed. |
==About this Structure== | ==About this Structure== | ||
| Line 26: | Line 26: | ||
[[Category: thiamine pyrophosphate]] | [[Category: thiamine pyrophosphate]] | ||
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 18:12:15 2008'' |
Revision as of 16:12, 21 February 2008
|
Crystal structure of phenylpyruvate decarboxylase of Azospirillum brasilense
Overview
Phenylpyruvate decarboxylase (PPDC) of Azospirillum brasilense, involved in the biosynthesis of the plant hormone indole-3-acetic acid and the antimicrobial compound phenylacetic acid, is a thiamine diphosphate-dependent enzyme that catalyses the nonoxidative decarboxylation of indole- and phenylpyruvate. Analogous to yeast pyruvate decarboxylases, PPDC is subject to allosteric substrate activation, showing sigmoidal v versus [S] plots. The present paper reports the crystal structure of this enzyme determined at 1.5 A resolution. The subunit architecture of PPDC is characteristic for other members of the pyruvate oxidase family, with each subunit consisting of three domains with an open alpha/beta topology. An active site loop, bearing the catalytic residues His112 and His113, could not be modelled due to flexibility. The biological tetramer is best described as an asymmetric dimer of dimers. A cysteine residue that has been suggested as the site for regulatory substrate binding in yeast pyruvate decarboxylase is not conserved, requiring a different mechanism for allosteric substrate activation in PPDC. Only minor changes occur in the interactions with the cofactors, thiamine diphosphate and Mg2+, compared to pyruvate decarboxylase. A greater diversity is observed in the substrate binding pocket accounting for the difference in substrate specificity. Moreover, a catalytically important glutamate residue conserved in nearly all decarboxylases is replaced by a leucine in PPDC. The consequences of these differences in terms of the catalytic and regulatory mechanism of PPDC are discussed.
About this Structure
2NXW is a Single protein structure of sequence from Azospirillum brasilense with , , and as ligands. Active as Phenylpyruvate decarboxylase, with EC number 4.1.1.43 Full crystallographic information is available from OCA.
Reference
The crystal structure of phenylpyruvate decarboxylase from Azospirillum brasilense at 1.5 A resolution. Implications for its catalytic and regulatory mechanism., Versees W, Spaepen S, Vanderleyden J, Steyaert J, FEBS J. 2007 May;274(9):2363-75. Epub 2007 Mar 30. PMID:17403037
Page seeded by OCA on Thu Feb 21 18:12:15 2008
