Characterization of Phenylpyruvate Decarboxylase, Involved in Auxin Production of Azospirillum brasilense

Abstract

). An ipdC-knockout mutant was found to produce only 10% (wt/vol) of the wild-type IAA production level. In this study, the encoded enzyme is characterized via a biochemical and phylogenetic analysis. Therefore, the recombinant enzyme was expressed and purified via heterologous overexpression in Escherichia coli and subsequent affinity chromatography. The molecular mass of the holoenzyme was determined by size-exclusion chromatography, suggesting a tetrameric structure, which is typical for 2-keto acid decarboxylases. The enzyme shows the highest k cat value for phenylpyruvate. Comparing values for the specificity constant k cat /K m , indole-3-pyruvate is converted 10-fold less efficiently, while no activity could be detected with benzoylformate. The enzyme shows pronounced substrate activation with indole-3-pyruvate and some other aromatic substrates, while for phenylpyruvate it appears to obey classical Michaelis-Menten kinetics. Based on these data, we propose a reclassification of the ipdC gene product of A. brasilense as a phenylpyruvate decarboxylase (EC 4.1

Genetic Analysis of the Upper Phenylacetate Catabolic Pathway in the Production of Tropodithietic Acid by Phaeobacter gallaeciensis

“…A catabolic route via free phenylacetate as described for Thauera aromatica (41) or Aromatoleum aromaticum EbN1 (54), however, does not exist in strain DSM 17395. This is also supported by a lack of genes in the genome of strain DSM 17395 encoding a phenylpyruvate decarboxylase, such as pdc of strain EbN1 (54) or ipdC of Azospirillum brasilense (46). Growth of the ior1 mutant on tyrosine and tryptophan indicated that ior1 is not essential for the catabolism of other aromatic amino acids, but this does not exclude the possibility that Ior1 can convert other aryl pyruvates such as indolepyruvate and p-hydroxyphenylpyruvate, like the archaeal IOR (23).…”

Production of Aromatic Compounds by Metabolically Engineered Escherichia coli with an Expanded Shikimate Pathway

“…The enzyme encoded by the ipdC gene derived from Azospirillum brasilense has been extensively investigated, and its threedimensional structure has been published (35,42). The enzyme acts not only on PP but also on 4HPP to produce the corresponding aldehydes.…”

Symbiosis as a General Principle in Eukaryotic Evolution

“…As the term suggests, PGPRs are associated with plant roots and promote plant growth. The underlying processes are complex and variable, but very commonly involve the capacity to synthesize signaling molecules, including plant hormones, for example, the auxin indole-3-acetic acid (IAA), and volatiles, for example, 2,3-butanediol (Spaepen et al 2007;Lugtenberg and Kamilova 2009;Roca et al 2013). The best-studied interaction relates to PGPR-derived IAA, which triggers increased root branching and a higher densi-ty of root hairs.…”