Molecular basis for the maintenance of envelope integrity in Selenomonas ruminantium: Cadaverine biosynthesis and covalent modification into the peptidoglycan play a major role

Seiji K. Ojima, Yoshiyuki K. Amio

Research output: Contribution to journalReview article

7 Citations (Scopus)

Abstract

Polyamine is a small organic polycation composed of a hydrocarbon backbone with multiple amino groups which ubiquitously exists in all living organisms from bacteria to higher animals. The critical step of polyamine biosynthesis generally includes the amino acid-decarboxylating reaction to produce the primary diamines, such as a synthesis of putrescine (NH3+ ·(CH2)4 ·NH3+) from ornithine, and cadaverine (NH3+ ·(CH2)5 ·NH3+) from lysine, which are catalyzed by pyridoxal-5′ -phosphate (PLP; vitamin B6)-dependent decarboxylases. Synthesized polyamines are implicated in a wide variety of cytoplasmic reactions such as DNA replication and protein synthesis, and are essential for proper growth of the organisms. However, in Selenomonas ruminantium, a strictly anaerobic Gram-negative bacterium dominant in sheep rumen, cadaverine displays its function in a quite distinctive scheme compared to the general bacteria reported. It serves as an essential constituent of the peptidoglycan for the maintenance of envelope integrity through an interaction with the periplasm-exposed SLH domain of Mep45, the outer membrane protein of this bacterium. Furthermore, cytoplasmic biosynthesis of cadaverine occurs totally in a eukaryotic-like manner rather than in a conventional way of bacteria. Lysine/ornithine decarboxylase (LDC/ODC), a PLP-dependent enzyme responsible for cadaverine synthesis in this bacterium, displays significant homology to the eukaryotic ODC but not to the general bacterial LDC nor ODC, and its activity is tightly regulated by antizyme-mediated proteolysis, a regulatory process generally found in eukaryotes. These findings represent the biological diversity of this bacterium beyond the preexisting knowledge related to the polyamine-physiology, cell envelope-architecture, and the regulatory system for the enzyme. In this review we will describe (i) the cadaverine-containing peptidoglycan of S. ruminantium: its chemical structure, biosynthesis, and biological function, and (ii) cellular biosynthesis of cadaverine by LDC/ODC and its antizyme-mediated regulation. In addition, we will briefly refer to (iii) the phylogenetic position and characteristics of S. ruminantium and its unique cadaverine-physiology.

Original languageEnglish
Pages (from-to)153-160
Number of pages8
JournalJournal of nutritional science and vitaminology
Volume58
Issue number3
DOIs
Publication statusPublished - 2012 Jan 1

Keywords

  • Antizyme-mediated proteolysis
  • Cadaverine-containing peptidoglycan
  • Cell envelope integrity
  • Lysine decarboxylase
  • Selenomonas ruminantium

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Nutrition and Dietetics

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