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Toxic peptide antibiotic

Cycioheptamycin - peptide antibiotic Amino acid is toxic and teratogenic... [Pg.42]

Bacitracin (Fig. 4) is a cyclic peptide antibiotic. The lipid II molecule involved in the bacterial cell wall biosynthesis has a C55 isoprenyl pyrophosphate moiety that must be dephosphorylated so that it can reparticipate in another round of lipid II transfer. Bacitracin binds to the isoprenyl pyrophosphate and prevents the dephosphorylation which, in turn, blocks cell wall growth by interfering with the release of the muropeptide subunits to the outside of the bacterial cell membrane. Bacitracin inhibits similar reactions in eukaryotic cells. So, it is systemically toxic but is an effective and widely used topical antibiotic. [Pg.359]

How do antibiotics act Some, like penicillin, block specific enzymes. Peptide antibiotics often form complexes with metal ions (Fig. 8-22) and disrupt the control of ion permeability in bacterial membranes. Polyene antibiotics interfere with proton and ion transport in fungal membranes. Tetracyclines and many other antibiotics interfere directly with protein synthesis (Box 29-B). Others intercalate into DNA molecules (Fig. 5-23 Box 28-A). There is no single mode of action. The search for suitable antibiotics for human use consists in finding compounds highly toxic to infective organisms but with low toxicity to human cells. [Pg.1164]

Peptide antibiotics are not often the drags of first choice for systemic therapy of important human disease. However, the World Health Organization, which chooses drags especially for Third World use based on efficacy, safety, quality, price, and availability, includes as essential such peptide antibiotics as bleomycin, dactinomycin, and bacitracin (as an ointment containing neomycin), plus several /8-lactams. See also Antibiotics, Antibiotics -Lactams. Systemic use of peptide antibiotics is many times limited by nephroloxicity and other toxicities. Semisynthesis or complete chemical synthesis of analogues of peptide antibiotics has most often not resulted in improved drags. [Pg.127]

Peptide antibiotics are composed of the peptide chain of amino acids, d and l, covalently linked to other moieties. Most peptides are toxic and are poorly absorbed from the alimentary tract. Peptide antibiotics are difficult to analyze in biological and food samples, as they are similar to matrix components. They can be separated on silica gel, amino silica gel, and silanized silica gel plates. A variety of mobile phases are applied, from a simple one like chloroform-methanol to a multicomponent one like n-butanol-butyl acetate-... [Pg.166]

Some antibiotics that have been derived from peptides were mentioned in Chapter l. The biosynthesis of penicillins was discussed in Chapter 8. Many peptide antibiotics are known. Some find clinical applications but others such as gramicidin S (9.7), tyrocidine A (9.8) and polymyxins (9.9) are too toxic for use in humans. Cyclosporin A (Figure 1.4), however, has immunosuppressive properties and it has been used in transplant surgery for this reason rather than for its antibiotic properties. Peptide antibiotics have some non-standard structural features and these may explain in part their antibiotic properties. First, cyclic peptides are not found in animal cells. Secondly, peptide antibiotics usually contain some unusual amino acids they may have the d configuration, be A-methylated or have other non-standard structural features. Clearly, these features are not compatible with direct ribo-somal synthesis. [Pg.217]

A third reason for this lack of knowledge may be the present limited therapeutic importance of the peptide antibiotics, mainly as a result of their narrow antimicrobial spectrum and their relatively high toxicity. However, the recent increase in serious infections caused by gram-negative bacteria and their growing resistance to the broad spectrum antibiotics has turned interest to some of the peptide antibiotics, which are the most active inhibitors of these organisms. [Pg.1]

An analogous mechanism in the mammalian cell may explain the high toxicity of these peptide antibiotics. Their specific nephrotoxicity may be due either to a difference of the structure between renal cell membranes and those in other cells or it may be due to the high concentration of the antibiotics in the renal system. [Pg.45]

Actinomycins, peptide antibiotics produced by various strains of Streptomyces. Actinomycins are orange-red bacteriostatic and cytostatic, but highly toxic, chromopeptides. The chromophore actinocin,... [Pg.5]

P. occur widely and have many different biological functions. Many are hormones, e.g. Corticotropin, Melanotropin, Oxytodn, Vasopressin, Releasing hormones, Insulin, Glucagon, Gastrin, Secretin, Angiotensin, Bradykinin, Endorphins, Opioid peptides (see entries for each of these). Many microorganisms produce P., often with antibiotic activity (see Peptide antibiotics). Some P. are very toxic, e.g. Phallotoxins (see), Amatoxins (see) and Melittin (see). Very simple P. are... [Pg.490]

The conformational features of ring-structure, hypercyclization, the presence of N-methyl amino acids and other imino acidsare not the attributes of peptide antibiotics only. The toxic principles of Amanita phalloides, phalloidin and amanitin exhibit similar characteristics and the more recently discovered and synthesized component of the same fungus antaminid (III), a peptide which can antagonize the toxic effects of amanitin, is also cyclic. In this particular case no D-amino... [Pg.267]


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See also in sourсe #XX -- [ Pg.261 ]




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