Enzymatic Synthesis of the Peptide in Bacterial Uridine Nucleotides

An enzyme from Bacillus subtilis which catalyzes the hydrolysis of UDP-MurNAc-pentapeptide to UDP-MurNAc-tripeptide and dalanyl-d-alanine has been purified. Heat-stable cofactors required for the hydrolysis were identified as Co++, ADP, and inorganic phosphate. The purified enzyme also catalyzes the ATP- and Mg++-dependent addition of d-alanyl-d-alanine to UDP-MurNAc-tripeptide, and the two activities were purified together. No synthesis of ATP was observed during hydrolysis in the presence of Co++, ADP, and Pi. The hydrolysis does not appear to be a simple reversal of synthesis. Studies on the mechanism of the hydrolysis are reported. Two other enzymes involved in the synthesis of peptide bonds in UDP-MurNAc-pentapeptide catalyzed hydrolytic reactions under similar conditions.