Peptidoglycan endopeptidase

D,D-endopeptidase acting on maturing peptidoglycan D, D - c arb o xyp ep tidase transpeptidation is absent none apparent... 

Extensive investigations of the properties of PBPs of E. coli, strain K12, were carried out. The results are indicative of our present understanding of PBPs and will be outlined. It should be stated that it is now understood that penicillin-sensitive enzymes such as DD-Cbase, peptidoglycan transpeptidase, and endopeptidases identified earlier are almost certainly identical with the PBPs under discussion here. Multiple PBPs have been discovered in all bacterial membranes studied. It is also now apparent that the interactions of (3-lactam antibiotics with bacteria can result in one or more effects on the physiology and structure of the cell. Thus inhibition of cell division can be observed so can lysis, bulge formation, or even the development of ovoid cell forms stable to osmosis. 

Figure 1.1 Electron Micrograph Showing Isolated Purified Sacculi from Escherichia coii. 1 and 2 show the purified sacculi which is in effect one enormous peptidoglycan molecule, 3 and 4 show the sacculi after treatment with specific endopeptidase. it can be seen that the giycan chains appear to run perpendicular to the long axis of the cell. Reproduced by permission, Verwer, R.W., Nanniga, N., Keck, W. and Schwartz, U. (1978) J. BacterioL, 136, 723.

Study of the penicillin binding proteins has shown that bacteria contain several different enzymes (transpeptidases, endopeptidases and carboxy-peptidases) each involved with a separate aspect of peptidoglycan... 

The three enzymes sensitive to penicillins, i.e., peptidoglycan transpeptidase, D-alanine earboxypeptldase, and endopeptidase, were not inhibited at bactericidal concentrations of FL 1060 , but the formation of peptido-glycans covalently bound to the cell wall or to lipoproteins was impaired. 

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