Abstract
Abstract Phospho-N-acetylmuramyl-pentapeptide translocase (UDP-MurNAc-Ala-γdGlu-Lys-dAla-dAla:undecaprenylphosphate phospho-MurNAc-pentapeptide transferase) catalyzes the initial membrane reaction in the biosynthesis of peptidoglycan. In addition, the enzyme catalyzes the exchange of [3H]uridine monophosphate with the uridine monophosphate moiety of UDP-MurNAc-pentapeptide. A specificity profile towards the peptide subunit of UDP-MurNAc-pentapeptide has been established for the exchange and transfer reactions catalyzed by the translocase from Staphylococcus aureus Copenhagen. A good correlation between Vmax/Km in the transfer reaction and Rmax/Km in the exchange reaction was observed. On the basis of glycine substitution, the enzyme has a high specificity for l-alanine in position 1 (R1) and d-alanine in position 4 (R4) and a low specificity for d-alanine in position 5 (R5). For example, when compared with UDP-MurNAc-Ala-dGlu-Lys-dAla-dAla, glycine replacement in either R1 or R4 results in a 9- and 15-fold decrease in Vmax/Km, respectively. In contrast, glycine substitution in R5 results in only a 1.5-fold decrease in Vmax/Km. These results are further supported by comparing UDP-MurNAc-Ala-dGlu-Lys-dAla-dAla, -Ala-dGlu-Lys-dAla, and -Ala-dGlu-Lys. For UDP-MurNAc-tetrapeptide a 4-fold decrease in Vmax/Km was observed whereas a 77-fold decrease was found for the -tripeptide. Replacement of both R1 and R4 by glycine reduces Rmax/Km 135-fold. The translocase has a low specificity for the diamino acid in R3. Substitution of lysine with meso-diaminopimelic acid results in a 1.5-fold decrease in Rmax/Km and with ornithine in no change. The established specificity profile of the translocase is consistent with the in vivo effects of elevated concentrations of glycine on the growth of S. aureus Copenhagen (Hammes, W., Schleifer, K.H., and Kandler, O. (1973) J. Bacteriol., 116, 1029–1053). Thus, it is suggested that the translocase has a key role in selecting analogs of UDP-MurNAc-Ala-γdGlu-Lys-dAla-dAla for peptidoglycan synthesis.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
