The critical role of the aldehyde dehydrogenase PauC in spermine, spermidine, and diaminopropane toxicity in Pseudomonas aeruginosa: Its possible use as a drug target

Abstract

The opportunistic human pathogen Pseudomonas aeruginosa exhibits great resistance to antibiotics; so, new therapeutic agents are urgently needed. Since polyamines levels are incremented in infected tissues, we explored whether the formation of a toxic aldehyde in polyamines degradation can be exploited in combating infection. We cloned the gene encoding the only aminoaldehyde dehydrogenase involved in P. aeruginosa polyamines‐degradation routes, PaPauC, overexpressed this enzyme, and found that it oxidizes 3‐aminopropionaldehyde (APAL) and 3‐glutamyl‐3‐aminopropionaldehyde (GluAPAL) − produced in spermine (Spm), spermidine (Spd), and diaminopropane (Dap) degradation, as well as 4‐aminobutyraldehyde (ABAL) and 4‐glutamyl‐4‐aminobutyraldehyde (GluABAL) − formed in putrescine (Put) degradation. As the catalytic efficiency of PaPauC with APAL was 30‐times lower than with GluAPAL, and GluAPAL is predominantly formed, APAL will be poorly oxidized ‘in vivo’. We found polyamines‐induced increases in the PaPauC activity of cell crude‐extracts and in the expression of the PapauC gene that were diminished by glucose. Spm, Spd, or Dap, but not Put, were toxic to P. aeruginosa even in the presence of other carbon and nitrogen sources, particularly to a strain with the PapauC gene disrupted. APAL, but not GluAPAL, was highly toxic even to wild‐type cells, suggesting that its accumulation, particularly in the absence of, or low, PaPauC activity is responsible for the toxicity of Spm, Spd, and Dap. Our results shed light on the toxicity mechanism of these three polyamines and strongly support the critical role of PaPauC in this toxicity. Thus, PaPauC emerges as a novel potential drug target whose inhibition might help in combating infection by this important pathogen.

Polyamine and Ethanolamine Metabolism in Bacteria as an Important Component of Nitrogen Assimilation for Survival and Pathogenicity

“…In P. aeruginosa PAO1, the gamma-glutamylation pathway ( Figure 3 , GGP) includes almost identical metabolic steps as that in E. coli [ 196 , 212 ], but is represented by seven pauA genes, four pauB genes, one pauC gene, and two pauD genes that are thought to be responsible for polyamine catabolism [ 195 , 196 ] ( Table 1 ). Interestingly, each PauA1-PauA7 enzyme seems to have different substrate specificity towards different mono- and polyamines being involved in the first step of the pathway [ 195 , 196 ].…”

“…The aminotransferase pathway ( Figure 3 , AMTP) of P. aeruginosa PAO1 includes a putrescine-pyruvate aminotransferase that generates γ-aminobutyraldehyde and L-alanine [ 213 , 214 ]. The KauB protein that corresponds to PatD from E. coli oxidizes in the following step, with γ-aminobutyraldehyde forming GABA, which is further catabolized to succinate by GabT and GabD [ 14 , 212 ] ( Figure 3 , AMTP; Table 1 ).…”

“…It requires an amine oxidase [ 195 , 215 , 216 , 217 , 218 , 219 ] ( Figure 3 , DOP). The spermine/spermidine dehydrogenase pathway has been described in P. aeruginosa [ 195 , 212 ], for which the structure of the essential enzyme spermidine dehydrogenase has been reported [ 216 ] ( Figure 3 , SPDP). In P. aeruginosa PAO1, the spermidine dehydrogenase (SpdH) can cleave spermidine into 1,3-diaminopropane and γ-aminobutyraldehyde and spermine into spermidine and 3-aminopropanaldehyde.…”

“…In P. aeruginosa PAO1, the spermidine dehydrogenase (SpdH) can cleave spermidine into 1,3-diaminopropane and γ-aminobutyraldehyde and spermine into spermidine and 3-aminopropanaldehyde. KauB oxidizes 3-aminopropanaldehyde to β-alanine, which is further catabolized to acetyl-CoA [ 195 , 212 ] ( Table 1 ).…”

“…Dashed arrows represent predicted and straight arrows confirmed metabolic pathways. Pathways described for the following bacteria—in black: E. coli , P. aeruginosa , and S. coelicolor ; dashed orange box: P. aeruginosa ; dashed brown box: S. aureus and P. aeruginosa ; dashed blue box: E. coli , B. subtilis , and C. glutamicum [ 7 , 14 , 195 , 197 , 198 , 201 , 206 , 207 , 208 , 212 , 215 , 217 , 218 , 219 ]. …”