The role of two families of bacterial enzymes in putrescine synthesis from agmatine via agmatine deiminase

Abstract

Putrescine, one of the main biogenic amines associated to microbial food spoilage, can be formed by bacteriafrom arginine via ornithine decarboxylase (ODC), or from agmatine via agmatine deiminase (AgDI). This study aims to correlate putrescine production from agmatine to the pathway involving N-carbamoylputrescine formation via AdDI (the aguAproduct) and N-carbamoylputrescine amidohydrolase (the aguB product), or putrescine carbamoyltransferase (the ptcA product) in bacteria. PCR methods were developed to detect the two genes involved in putrescine production from agmatine.Putrescine production from agmatine could be linked to the  aguA and  ptcA genes in  Lactobacillus hilgardii X1B,Enterococcus faecalis ATCC 11700, and Bacillus cereus ATCC 14579. By contrast Lactobacillus sakei 23K was unable toproduce putrescine, and although a fragment of DNA corresponding to the gene aguA was amplified, no amplification wasobserved for the ptcA gene. Pseudomonasaeruginosa PAO1 produces putrescine and is reported to harbour aguA and aguBgenes, responsible for agmatine deiminase and N-carbamoylputrescine amidohydrolase activities. The enzyme from P. aeruginosa PAO1 that converts N-carbamoylputrescine to putrescine (the aguB product) is different from other microorganismsstudied (the ptcA product). Therefore, the aguB gene from P. aeruginosa PAO1 could not be amplified with ptcA specificprimers. The aguB and ptcA genes have frequently been erroneously annotated in the past, as in fact these two enzymes areneither homologous nor analogous. Furthermore, the aguA, aguB and ptcA sequences available from GenBank were subjected to phylogenetic analysis, revealing that gram-positive bacteria harboured ptcA, whereas gram-negative bacteria harbouraguB. This paper also discusses the role of the agmatine deiminase system (AgDS) in acid stress resistance.