Enzymatic Synthesis of the Peptide in Bacterial Uridine Nucleotides. Iv. Purification and Properties of D-glutamic Acid-adding Enzyme.

The pentapeptide moiety of uridine diphosphate acetylmuramyl-pentapeptide, a precursor of the peptidoglycan of bacterial cell walls, is synthesized in a reaction sequence involving five enzymes. The amount and specificity of these enzymes have been studied in 10 microorganisms, five of which contain L-lysine as the third amino acid in the peptide sequence, and five of which contain instead mesodiaminopimelic acid. The former five contain an L-lysineadding enzyme specific for that amino acid, and the latter five contain a similarly specific meso-diaminopimelic acidadding enzyme. The fifth enzyme which catalyzes the addition of D-alanyl-n-alanine to UDP-MurNAc-tripeptide is less specific for the occurrence of L-lysine or meso-diaminopimelic acid in the tripeptide moiety. The rate-limiting catalyst in the sequence may be the first enzyme, the Lalanine-adding enzyme. In addition, the analyses of some uridine nucleotides obtained from several diaminopimelic acid-containing organisms are presented.