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 and 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: [formula: see text] The pentapeptide structure was identical to that of the peptide subunit of the intact pseudomurein except one additional alanine residue, which is split off during further processing. The pentapeptide synthesis starts with glutamic acid, which is phosphorylated at the N alpha-amino group. N alpha-phosphoryl-glutamic acid is transferred to a nucleotide-carrier, forming N alpha-UDP-glutamic acid. The further pentapeptide biosynthesis is achieved via a di-, tri- and tetrapeptide by stepwise addition of the corresponding amino acids.