The peptidoglycan crosslinking enzyme system in Streptomyces strains R61, K15 and rimosus

in European Journal of Biochemistry (1977), 81(1), 33-44

The transpeptidation reaction performed by the membranes of Streptomyces strain R61 fits the general rate equation for an enzyme-catalysed bimolecular reaction. The same membranes (E) interact with beta ... [more ▼]

The transpeptidation reaction performed by the membranes of Streptomyces strain R61 fits the general rate equation for an enzyme-catalysed bimolecular reaction. The same membranes (E) interact with beta-lactams (I) to form inactive penicillin-enzyme-membrane complexes (EI) of rather high stability, which subsequently break down (E + I leads to EI leads to E + degradation products). The enzyme is regenerated and the antibiotic is released in the form of an inactive metabolite. With benzylpenicillin, the degradation product is benzylpenicilloic acid. The reaction is heat-labile. The first step of the reaction (E + I leads to EI) is characterized by a second-order rate constant (kformation in M-1 s-1) and the second step (EI leads to E + degradation products) by a first-order rate constant (kbreakdown in s-1). The effects in vitro of various beta-lactams on the membrane-bound transpeptidase, as expressed by the relevant kformation and kbreakdown values, parallel the effects in vivo of the same antibiotics as expressed by their ability to prevent the germination and growth of conidiospores. The kinetic parameters of the transpeptidase that was solubilized with N-cetyl-N,N,N-trimethylammonium bromide with respect to its interaction with both peptide substrates and beta-lactam antibiotics are quantitatively different from those of the membrane-bound enzyme. Moreover, the solubilized enzyme fragments benzylpenicillin with formation of phenylacetylglycine, a reaction which is similar to that catalysed by the exocellular R61 enzyme. The membranes of Streptomyces strains rimosus and K15 possess an active 'classic' penicillinase. They were not studied but the kinetic coefficients of the corresponding solubilized transpeptidases were determined and compared with those of the solubilized enzyme from strain R61. [less ▲]

The concept of the penicillin target from 1965 until today. The thirteenth marjory stephenson memorial lecture

in Journal of General Microbiology (1977, July 01), 101(1), 13-33

Interactions between beta-lactam antibiotics and isolated membranes of Streptococcus faecalis ATCC 9790

in European Journal of Biochemistry (1977), 75(1), 231-239

The DD-carboxypeptidase-exchange membrane-bound enzyme in Streptococcus faecalis ATCC 9790 reacts with beta-lactam antibiotics to form complexes with rather long half-lives. Depending upon the antibiotic ... [more ▼]

The DD-carboxypeptidase-exchange membrane-bound enzyme in Streptococcus faecalis ATCC 9790 reacts with beta-lactam antibiotics to form complexes with rather long half-lives. Depending upon the antibiotic, the second-order rate constants for complex formation range from 0.75-560 M-1 S-1 (at 37 degrees C and in water) and the first-order rate constants for complex breakdown range from 1.3 to 26 x 10(-5) s-1 (at 37 degrees C and in 5 mM phosphate buffer pH 7.5). There are about 30 pmol of DD-carboxypeptidase-exchange enzyme per mg of membrane protein. The degradation products arising from benzylpenicillin are phenylacetylglycine and probably N-formyl-D-penicillamine. Isolated membranes also contain other penicillin binding sites (about 70 pmol/mg membrane protein). That part of benzylpenicillin which reacts with at least some of these latter sites is slowly degraded into penicilloic acid. Normal functioning of the DD-carboxypeptidase-exchange membrane-bound enzyme is important, if not essential, for cell growth. With the beta-lactam antibiotics tested inhibition of cell growth is mainly related to the rates of formation of the inactive enzyme-antibiotic complexes. The relationship, however, is not a direct one probably due to the competitive effect exerted by the other penicillin binding sites. [less ▲]

The bacterial DD-carboxypeptidase-transpeptidase enzyme system : a new insight into the mode of action of penicillin

Book published by University of Tokyo Press (1977)

Le récepteur de la penicilline chez les bactéries

in Bulletin de l'Académie Royale de Médecine de Belgique (1977), 132(1), 101-108

The β-lactam antibiotics are both substrates and inhibitors of the DD-carboxypeptidase-transpeptidase enzyme system involved in the closure of the interpeptide bridges during the biosynthesis of the wall ... [more ▼]

The β-lactam antibiotics are both substrates and inhibitors of the DD-carboxypeptidase-transpeptidase enzyme system involved in the closure of the interpeptide bridges during the biosynthesis of the wall peptidoglycan in bacteria. [less ▲]

Biosynthesis and assembly of bacterial cell walls

in Poste, George; Nicolson, Garth L (Eds.) The synthesis, assembly and turnover of celle surface components. Cell surface review. vol. 4 (1977)

Mode of interaction between beta-lactam antibiotics and the exocellular DD-carboxypeptidase--transpeptidase from Streptomyces R39

in Biochemical Journal (1976), 155(3), 623-629

The exocellular DD-carboxypeptidase-transpeptidase of Streptomyces R39 is inhibited by beta-lactam antibiotics according to the same general scheme of reaction as the exocellular DD-carboxypeptidase ... [more ▼]

The exocellular DD-carboxypeptidase-transpeptidase of Streptomyces R39 is inhibited by beta-lactam antibiotics according to the same general scheme of reaction as the exocellular DD-carboxypeptidase-transpeptidase of Streptomyces R61. However, the values for the kinetic constants involved in the reaction are very different for the two enzymes and provide an explanation for the observation that the R39 enzyme is more sensitive to beta-lactam antibiotics than the R61 enzyme. Further, particular beta-lactams influence the kinetic constants to different extents depending on the source of the enzyme, so that a physical basis for the spectrum of antibiotic activity against particular enzyme systems is provided. [less ▲]

The direction of peptide trimer synthesis from the donor-acceptor substrate Nalpha-(acetyl)-Nepsilon-(glycyl)-L-lysyl-D-alanyl-D-alanine by the exocellular dd-carboxypeptidase-transpeptidase of Streptomyces R61

in FEBS Letters (1976), 63(1), 112-116

Exocellular DD-carboxypeptidases-transpeptidases from Streptomyces

in Methods in Enzymology (1976), 45

Degradation of benzylpenicillin by the exocellular DD-carboxypeptidase-transpeptidase from Streptomyces R 61

in Archives Internationales de Physiologie et de Biochimie (1975), 83(5), 905-907