? Cell wall is indispensable for survival of bacteria. The building blocks of the bacterial peptidoglycan, the major constituent of cell wall, are assembled within the cytoplasm, then they are transported to the surface of the cytoplasmic membrane. The final steps of cell wall assembly take place on the cytoplasmic membrane by a set of enzymes referred to as penicillin-binding proteins (PBPs). The naming of these enzymes stems from the determination that they serve as the targets for beta-lactam antibiotics (penicillins, cephalosporins, etc.). Three important biochemical activities for PBPs are the transglycosylase, DD-transpeptidase and DD-carboxypeptidase activities. Investigations of these enzymic activities are disclosed in this grant application.
Three Specific Aims are offered.
Specific Aim 1 is to study the reactions of both the bifunctional and monofunctional DD-transpeptidases.
Specific Aim 2 describes the detailed studies of the reactions of two DD-carboxypeptidases. Synthetic substrates that closely mimic the polymeric substrates for these enzymes have been developed in the Mobashery lab for detailed study of the microscopic steps of the reactions of these enzymes. Furthermore, computational studies are outlined to elucidate the details of the reactions of these enzymes.
Specific Aim 3 will be the continuation of the efforts in development of non-beta-lactam inhibitors for PBPs as potential antibiotics. Currently only beta-lactams are used clinically in inhibition of these enzymes, but beta-lactams may be facing obsolescence in the near future because of widespread resistance to them. Three classes of non-beta-lactam leads for inhibition of PBPs have been identified and will be the subjects of study by generation of focused libraries of related compounds in quest for the desired non- beta-lactam antibiotics that target PBPs for inhibition. It is expected that the outcome of these studies will shed definitive light on the biochemical mechanisms of PBPs and pave the way for discoveries of novel inhibitors as potential future antibiotics. ? ? ?
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