The davDT Operon of Pseudomonas putida , Involved in Lysine Catabolism, Is Induced in Response to the Pathway Intermediate δ-Aminovaleric Acid

Abstract

Pseudomonas putida KT2440 is a soil microorganism that attaches to seeds and efficiently colonizes the plant's rhizosphere. Lysine is one of the major compounds in root exudates, and P. putida KT2440 uses this amino acid as a source of carbon, nitrogen, and energy. Lysine is channeled to ␦-aminovaleric acid and then further degraded to glutaric acid via the action of the davDT gene products. We show that the davDT genes form an operon transcribed from a single 70 -dependent promoter. The relatively high level of basal expression from the davD promoter increased about fourfold in response to the addition of exogenous lysine to the culture medium. However, the true inducer of this operon seems to be ␦-aminovaleric acid because in a mutant unable to metabolize lysine to ␦-aminovaleric acid, this compound, but not lysine, acted as an effector. Effective induction of the P. putida P davD promoter by exogenously added lysine requires efficient uptake of this amino acid, which seems to proceed by at least two uptake systems for basic amino acids that belong to the superfamily of ABC transporters. Mutants in these ABC uptake systems retained basal expression from the davD promoter but exhibited lower induction levels in response to exogenous lysine than the wild-type strain.

Molecular characterization of lysR-lysXE, gcdR-gcdHG and amaR-amaAB operons for lysine export and catabolism: a comprehensive lysine catabolic network in Pseudomonas aeruginosa PAO1

“…As shown in Fig. 1, L-lysine is catabolized via the monooxygenase pathway in Pseudomonas putida, while in Pseudomonas aeruginosa it is mainly mediated via the decarboxylase pathway (Chou et al, 2010;Revelles et al, 2004Revelles et al, , 2005. Expression of the lysine decarboxylase LdcA was found to be inducible by the arginine regulator ArgR and L-arginine but not L-lysine in P. aeruginosa PAO1 (Chou et al, 2010), making this initial step in the proposed pathway a bottleneck for L-lysine catabolism in this organism.…”

“…Cadaverine, the product of LdcA, is further degraded to 5-aminovalerate through the c-glutamylation pathway for polyamine catabolism that is controlled by PauR (Chou et al, 2013;Yao et al, 2011). Both monooxygenase and decarboxylase pathways converge at 5-aminovalerate, which is then converted to glutarate by a pair of transaminase and semialdehyde dehydrogenase encoded by the gabDT operon (Chou et al, 2013;Revelles et al, 2004). Glutarate is proposed to produce acetyl-CoA that can enter the Krebs cycle (Numa et al, 1964), and glutaryl-CoA dehydrogenase enzyme (an enzyme in glutarate catabolism) activity has been reported in crude extracts of P. aeruginosa (Fothergill & Guest, 1977).…”

Multiple and Interconnected Pathways for l -Lysine Catabolism in Pseudomonas putida KT2440

“…The davD promoter was expressed at a certain level in the absence of L-lysine, but its expression increased about fourfold in response to the addition of exogenous Llysine to the culture medium. However, the real inducer of this operon seems to be AMV because in a mutant unable to metabolize L-lysine to ␦-aminovalerate, this compound, and not L-lysine, acted as an effector (38).…”

“…In this route, the first step involves the oxidative decarboxylation of the amino acid to yield ␦-aminovaleramide, which is hydrolyzed to produce ammonium and ␦-aminovalerate. Thereafter, ␦-aminovalerate is converted into glutarate via glutarate semialdehyde (6,7) in reactions catalyzed by the products of the davD and the davT genes, the only genes of the pathway identified so far (11,38). The davD gene forms an operon with davT, the gene order being davDT (38).…”

“…Thereafter, ␦-aminovalerate is converted into glutarate via glutarate semialdehyde (6,7) in reactions catalyzed by the products of the davD and the davT genes, the only genes of the pathway identified so far (11,38). The davD gene forms an operon with davT, the gene order being davDT (38). The rei-2 mutant is a KT2440 derivative that is unable to use L-lysine as a carbon source and which was isolated after mutagenesis of the wild-type strain with mini-Tn5-Јlux.…”