title: Crystal structure of thiamindiphosphate-dependent indolepyruvate decarboxylase from Enterobacter cloacae, an enzyme involved in the biosynthesis of the plant hormone indole-3-acetic acid.
abstract: The thiamin diphosphate-dependent enzyme indolepyruvate decarboxylase catalyses the formation of indoleacetaldehyde from indolepyruvate, one step in the indolepyruvate pathway of biosynthesis of the plant hormone indole-3-acetic acid. The crystal structure of this enzyme from Enterobacter cloacae has been determined at 2.65 A resolution and refined to a crystallographic R-factor of 20.5% (Rfree 23.6%). The subunit of indolepyruvate decarboxylase contains three domains of open alpha/beta topology, which are similar in structure to that of pyruvate decarboxylase. The tetramer has pseudo 222 symmetry and can be described as a dimer of dimers. It resembles the tetramer of pyruvate decarboxylase from Zymomonas mobilis, but with a relative difference of 20 degrees in the angle between the two dimers. Active site residues are highly conserved in indolepyruvate/pyruvate decarboxylase, suggesting that the interactions with the cofactor thiamin diphosphate and the catalytic mechanisms are very similar. The substrate binding site in indolepyruvate decarboxylase contains a large hydrophobic pocket which can accommodate the bulky indole moiety of the substrate. In pyruvate decarboxylases this pocket is smaller in size and allows discrimination of larger vs. smaller substrates. In most pyruvate decarboxylases, restriction of cavity size is due to replacement of residues at three positions by large, hydrophobic amino acids such as tyrosine or tryptophan.
authors.affiliation: Institute of Biochemistry, Department of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Schütz
authors.forename: Tatyana
authors.initials: T
authors.lastname: Sandalova
authors.forename: Stefano
authors.initials: S
authors.lastname: Ricagno
authors.forename: Gerhard
authors.initials: G
authors.lastname: Hübner
authors.forename: Stephan
authors.initials: S
authors.lastname: König
authors.forename: Gunter
authors.initials: G
authors.lastname: Schneider
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002262:Carboxy-Lyases / Q000737:chemistry*; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004754:Enterobacter / Q000201:enzymology*; D004926:Escherichia coli / Q000378:metabolism; D007210:Indoleacetic Acids / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013835:Thiamine Pyrophosphate / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D007210:Indoleacetic Acids; C030737:indoleacetic acid; C068832:indolepyruvate decarboxylase; D002262:Carboxy-Lyases; D008274:Magnesium; D013835:Thiamine Pyrophosphate