2hbx

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Crystal Structure of alpha-Amino-beta-Carboxymuconate-epsilon-Semialdehye-Decarboxylase (ACMSD)

Overview

Alpha-amino-beta-carboxymuconate-epsilon-semialdehyde decarboxylase, (ACMSD) is a widespread enzyme found in many bacterial species and all, currently sequenced eukaryotic organisms. It occupies a key position at, the branching point of two metabolic pathways: the tryptophan to, quinolinate pathway and the bacterial 2-nitrobenzoic acid degradation, pathway. The activity of ACMSD determines whether the metabolites in both, pathways are converted to quinolinic acid for NAD biosynthesis or to, acetyl-CoA for the citric acid cycle. Here we report the first, high-resolution crystal structure of ACMSD from Pseudomonas fluorescens, which validates our previous predictions that this enzyme is a member of, the metal-dependent amidohydrolase superfamily of the (beta/alpha)(8) TIM, barrel fold. The structure of the enzyme in its native form, determined at, 1.65 A resolution, reveals the precise spatial arrangement of the active, site metal center and identifies a potential substrate-binding pocket. The, identity of the native active site metal was determined to be Zn. Also, determined was the structure of the enzyme complexed with cobalt at 2.50 A, resolution. The hydrogen bonding network around the metal center suggests, that Arg51 and His228 may play important roles in catalysis. The metal, center configuration of PfACMSD is very similar to that of Zn-dependent, adenosine deaminase and Fe-dependent cytosine deaminase, suggesting that, ACMSD may share certain similarities in its catalytic mechanism with these, enzymes. These data enable us to propose possible catalytic mechanisms for, ACMSD which appear to be unprecedented among all currently characterized, decarboxylases.

About this Structure

2HBX is a Single protein structure of sequence from Pseudomonas fluorescens with as ligand. Full crystallographic information is available from OCA.

Reference

Crystal structure of alpha-amino-beta-carboxymuconate-epsilon-semialdehyde decarboxylase: insight into the active site and catalytic mechanism of a novel decarboxylation reaction., Martynowski D, Eyobo Y, Li T, Yang K, Liu A, Zhang H, Biochemistry. 2006 Sep 5;45(35):10412-21. PMID:16939194

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