A NOVEL PATHWAY OF PEPTIDE BIOSYNTHESIS FOUND IN METHANOGENIC ARCHAEA

The peptide subunits of the pseudomurein, the cell-wall peptidoglycan of some methanogens, are usually composed of glutamic acid, alanine an d lysine. In order to get a more detailed picture of the biosynthetic pathway of the peptide subunit, we performed in vitro assays. Starting from glutamic acid a pentapeptide was obtained in seven steps: [GRAPH ICS] The pentapeptide structure was identical to that of the peptide s ubunit of the intact pseudomurein except one additional alanine residu e, which is split off during further processing. The pentapeptide synt hesis starts with glutamic acid, which is phosphorylated at the N-alph a-amino group. N-alpha-phosphoryl-glutamic acid is transferred to a nu cleotide-carrier, forming N-alpha-UDP-glutamic acid. The further penta peptide biosynthesis is achieved via a di-, tri- and tetrapeptide by s tepwise addition of the corresponding amino acids.