期刊
JOURNAL OF ORGANIC CHEMISTRY
卷 69, 期 3, 页码 778-784出版社
AMER CHEMICAL SOC
DOI: 10.1021/jo035397e
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资金
- NIGMS NIH HHS [GM 61629] Funding Source: Medline
The major constituent of the bacterial cell wall, peptidoglycan, is comprised of repeating units of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) with an appended peptide. Penicillin-binding proteins (PBPs) are involved in the final stages of bacterial cell wall assembly. Two activities for PBPs are the cross-linking of the cell wall, carried out by DD-transpeptidases, and the DD-peptidase activity, that removes the terminal D-Ala residue from peptidoglycan. The DD-peptidase activity moderates the extent of the cell wall cross-linking. There exists a balance between the two activities that is critical for the well-being of bacterial cells. We have cloned and purified PBP5 of Escherichia coli. The membrane anchor of this protein was removed, and the enzyme was obtained as a soluble protein. Two fragments of the polymeric cell wall of Gram-negative bacteria (compounds 5 and 6) were synthesized. These molecules served as substrates for PBP5. The products of the reactions of PBP5 and compounds 5 and 6 were isolated and were shown to be D-Ala and the fragments of the substrates minus the terminal D-Ala. The kinetic parameters for these enzymic reactions were evaluated. PBP5 would appear to have the potential for turnover of as many as 1.4 million peptidoglycan strands within a single doubling time (i.e., generation) of E. coli.
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