Transcriptome Analysis of Agmatine and Putrescine Catabolism inPseudomonas aeruginosaPAO1

Abstract

Polyamines (putrescine, spermidine, and spermine) are major organic polycations essential for a wide spectrum of cellular processes. The cells require mechanisms to maintain homeostasis of intracellular polyamines to prevent otherwise severe adverse effects. We performed a detailed transcriptome profile analysis of Pseudomonas aeruginosa in response to agmatine and putrescine with an emphasis in polyamine catabolism. Agmatine serves as the precursor compound for putrescine (and hence spermidine and spermine), which was proposed to convert into 4-aminobutyrate (GABA) and succinate before entering the tricarboxylic acid cycle in support of cell growth, as the sole source of carbon and nitrogen. Two acetylpolyamine amidohydrolases, AphA and AphB, were found to be involved in the conversion of agmatine into putrescine. Enzymatic products of AphA were confirmed by mass spectrometry analysis. Interestingly, the alanine-pyruvate cycle was shown to be indispensable for polyamine utilization. The newly identified dadRAX locus encoding the regulator alanine transaminase and racemase coupled with SpuC, the major putrescine-pyruvate transaminase, were key components to maintaining alanine homeostasis. Corresponding mutant strains were severely hampered in polyamine utilization. On the other hand, an alternative ␥-glutamylation pathway for the conversion of putrescine into GABA is present in some organisms. Subsequently, GabD, GabT, and PA5313 were identified for GABA utilization. The growth defect of the PA5313 gabT double mutant in GABA suggested the importance of these two transaminases. The succinic-semialdehyde dehydrogenase activity of GabD and its induction by GABA were also demonstrated in vitro. Polyamine utilization in general was proven to be independent of the PhoPQ two-component system, even though a modest induction of this operon was induced by polyamines. Multiple potent catabolic pathways, as depicted in this study, could serve pivotal roles in the control of intracellular polyamine levels.Agmatine, a cationic compound derived from arginine decarboxylation, serves as the precursor of three major polyamines, putrescine, spermidine, and spermine. These polyamines are the major organic polycations found in all living cells. Polyamines have pleiotropic effects on several cellular processes. In more complex organisms, these compounds are required for cell proliferation and differentiation (2). In Escherichia coli, these polycations play significant roles in the structural and functional organization of the chromosome (35). They are implicated in RNA synthesis through the stimulation of the activity of RNA polymerase and in protein synthesis through the stabilization of ribosomal structure and modulation of translational fidelity (9). In addition, polyamines are involved in the induction of recA in E. coli in response to UV or ␥ irradiation (14). Polyamines are thought to protect DNA from oxidative damage by serving as free radical scavengers (7, 13). Some microorganisms also use polyamines for the synthesis of se...

Comparative single-cell genomics reveals potential ecological niches for the freshwater acI Actinobacteria lineage

“…Other transporters that the 11 acI SAGs have in common, include ABC-type transporters for ribose/xylose/ arabinose/galactoside, polyamines, dipeptides and branched-chain amino acids ( Table 2). The polyamine transporters are likely being used for putrescine uptake, as the SAGs harbor downstream pathways for its eventual conversion to succinate via the transamination pathway (Dasu et al, 2006;Chou et al, 2008); (Figure 2). Genes for the uptake of carboxylic acids in acI-A1, acI-A7 and acI-B1 were not found in any of the sequenced genomes, consistent with MAR-FISH-based studies (Buck et al, 2009;Salcher et al, 2013).…”

Alternative Spermidine Biosynthetic Route Is Critical for Growth of Campylobacter jejuni and Is the Dominant Polyamine Pathway in Human Gut Microbiota

“…Even in polyamine biosynthesis, there is a precedent for bypassing metabolic blocks. The Pseudomonas aeruginosa PAO1 N-carbamoylputrescine amidohydrolase gene deletion produced a leaky biosynthetic phenotype, and it was consequently found that acetylputrescine amidohydrolase, which has a very similar substrate to N-carbamoylputrescine (26), is induced in the gene deletion mutant and allows bypass of the metabolic block. The CANSDH/ CASDH enzyme is related to homospermidine synthase, lysine 6-dehydrogenase, saccharopine dehydrogenase, and aspartate dehydrogenase (6).…”

Global Proteomics Reveal an Atypical Strategy for Carbon/Nitrogen Assimilation by a Cyanobacterium Under Diverse Environmental Perturbations

“…6, supplemental Table 8). Slr1022 shows strong similarity to the proteins (YgjG and SpuC) involved in degradation of putrescine into aminobutyrate in E. coli and Pseudomonas (55,56). Further evidence that succinate is produced from arginine came from the strong up-regulation of succinate dehydrogenase and malate dehydrogenase (Fig.…”

“…Putrescine is known to play a critical role in DNA, RNA, and protein synthesis, as well as in cell proliferation and differentiation. Furthermore, putrescine serves as a source for carbon and nitrogen in E. coli and Pseudomonas (55,56), where it is converted to succinate. Examination of proteins involved in putrescine degradation suggested that this pathway is also active in Synechocystis (Fig.…”