Portage of various compounds into bacteria by attachment to glycine residues in peptides

Abstract

Synthetic di-and oligopeptides are described that contain nucleophilic moieties attached to the a carbon of a glycine residue. These peptides are accepted by the peptide transport systems of Escherichia coli (and other microorganisms) and are capable of being hydrolyzed by intracellular peptidases. After liberation of its amino group the a-substituted glycine is chemically unstable (although it is stable in peptide form) and decomposes, releasing the nucleophilic moiety. Thus, the combined result of peptide transport and peptidase action is the intracellular release of the nucleophile. Peptides containing glycine residues a-substituted with thiophenol, aniline, or phenol are used as models for this type of peptideassisted entry and their metabolism by E. coli is described. Peptides of this type have broad applicability to the study of microbial physiology and the development of an additional class of antimicrobial agents.

Relative rates of transport of peptidyl drugs by Candida albicans

“…The detector peptide system (15,16) centers on the use of peptides containing ox-thiophenylglycine residues (alanyl-cx-thiophenylglycine and alanyl-cx-thiophenylglycylalanine) which are stable in the form of a peptide but which break down to release thiophenol after transport into the cell and intracellular hydrolysis by peptidases. Since transport of these peptides is rate limiting, it can be monitored by following the release of thiophenol by spectrophotometric detection with Ellman reagent (5,5'-diothiobis(2-nitrobenzoic acid).…”

“…However, quantitative data relating to the transport of these molecules or to how the large nucleoside side-chain residue affects the transport process have not been reported. We recently developed a new method (the detector peptide system) for monitoring peptide uptake in microorganisms (15,16), and we used this procedure to study the competitive effects observed at the transport system. In conjunction with the Technicon system for directly monitoring peptide uptake we were able to gain new Although the physical characteristics (acidity, basicity, lipophilicity, etc.)…”

Synthetic transport systems in bacteria

“…An alternative strategy involves coupling of cargo molecules to the α-carbon atom of a peptide's glycine residue [110]. Such α-substituted glycines are unstable in free form but become more stable when coupled to an N-terminal amino acid, for example in a peptide.…”

“…As for the previous approach, higher growth inhibiting effects were detected if the α-substituted glycine residues were part of tripeptides. The major drawback of this strategy is that, even if incorporated into a peptide, α-substituted glycines tend to be highly instable if they contain good leaving groups, resulting in a half-life of only several minutes [110].…”

“…In a different approach, nucleophilic compounds were attached to the α-carbon atom of a glycine residue in a tripeptide and transported into the cell via the Opp system. The α-substituted glycine is stable only if it is part of a peptide but will decompose rapidly once it is liberated by cytoplasmic peptidases, releasing the leaving group [110][111][112]. The drawback of this method is that those peptides which contain a glycine residue with substituents that can function as good leaving groups are rather instable and have a half-life of only several minutes, making the system difficult to use in practical terms [110].…”