Interaction of (2,3)-methylenepenams with penicillin-binding proteins.
A series of (2,3)-methylenepenams were examined with respect to binding to essential penicillin-binding proteins (PBPs) in Escherichia coli and Staphylococcus aureus. The compounds were also examined with respect to their interaction with Streptomyces strain R61 DD-carboxypeptidase. The alpha isomer of (2,3)-methylene penicillin G bound to PBP 3 of E. coli and other enterobacteria at 0.1 to 10 micrograms/ml. The beta isomer bound to PBP 3 at 100 micrograms/ml. Either isomer bound to PBPs 1b and 2 of E. coli only at 100 micrograms/ml. The alpha, but not the beta, isomer also bound to PBP 2 of S. aureus at 0.1 micrograms/ml. Binding studies with radiolabeled compounds indicated the binding to be covalent and revealed no additional binding proteins. (2,3)-Methylenepenams active against E. coli bound to PBP 3 and induced filamentation. The compounds also inhibited Streptomyces strain R61 DD-carboxypeptidase with apparent 50% inhibitory concentrations as low as 10(-7) M. The two (2,3)-methylene penicillin G isomers bound to the enzyme covalently, most likely at the same site as penicillin G since partial proteolysis after binding radiolabeled compounds produced similar peptide patterns. The bound beta isomer was released with a half-time similar to that of penicillin G (70 min at 30 degrees C), while the alpha isomer was released with a longer half-time (13 h at 30 degrees C). With either isomer, the major release product was phenylacetylglycine, suggesting C-5-C-6 cleavage.
Georgopapadakou
N H
NH
Roche Research Center, Nutley, New Jersey 07110.
Russo
D A
DA
Liebman
A
A
Burger
W
W
Rossman
P
P
Keith
D
D
D001426:Bacterial Proteins; D002268:Carboxypeptidases / Q000037:antagonists & inhibitors; D002352:Carrier Proteins / Q000378:metabolism*; D002512:Cephalothin / Q000494:pharmacology; D055598:Chemical Phenomena; D002621:Chemistry; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D006602:Hexosyltransferases; D007536:Isomerism; D002267:Muramoylpentapeptide Carboxypeptidase / Q000378:metabolism*; D046915:Penicillin-Binding Proteins; D010406:Penicillins / Q000378:metabolism* / Q000494:pharmacology; D010458:Peptidyl Transferases; D011485:Protein Binding; D013211:Staphylococcus aureus / Q000378:metabolism*; D013302:Streptomyces / Q000201:enzymology*
D001426:Bacterial Proteins; D002352:Carrier Proteins; D046915:Penicillin-Binding Proteins; D010406:Penicillins; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002268:Carboxypeptidases; D002267:Muramoylpentapeptide Carboxypeptidase; D002512:Cephalothin