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Tabtoxinine β-lactam
Tabtoxinine β-lactam is a monobactam antibiotic derived from tabtoxin. Unlike other β-lactam antibiotics, which inhibit penicillin-binding proteins Penicillin-binding proteins (PBPs) are a group of proteins that are characterized by their affinity for and binding of penicillin. They are a normal constituent of many bacteria; the name just reflects the way by which the protein was discove ..., tabtoxinine β-lactam inhibits glutamine synthetase. References Lactams Amino acid derivatives {{heterocyclic-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monobactam
Monobactams are monocyclic and bacterially-produced β-lactam antibiotics. The β-lactam ring is not fused to another ring, in contrast to most other β-lactams. Monobactams are effective only against aerobic Gram-negative bacteria (e.g., '' Neisseria'', ''Pseudomonas''). Siderophore-conjugated monobactams show promise for the treatment of multi drug-resistant pathogens. Aztreonam is a commercially available monobactam antibiotic. Other examples of monobactams are tigemonam, nocardicin A, and tabtoxin. Adverse effects to monobactams can include skin rash and occasional abnormal liver functions. Monobactam antibiotics exhibit no IgE cross-reactivity reactions with penicillin but have shown some cross reactivity with cephalosporin The cephalosporins (sg. ) are a class of β-lactam antibiotics originally derived from the fungus '' Acremonium'', which was previously known as ''Cephalosporium''. Together with cephamycins, they constitute a subgroup of β-lactam ant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antibiotic
An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy, treatment and antibiotic prophylaxis, prevention of such infections. They may either bactericide, kill or bacteriostatic agent, inhibit the growth of bacteria. A limited number of antibiotics also possess antiprotozoal activity. Antibiotics are not effective against viruses such as the common cold or influenza; drugs which inhibit viruses are termed antiviral drugs or antivirals rather than antibiotics. Sometimes, the term ''antibiotic''—literally "opposing life", from the Greek language, Greek roots ἀντι ''anti'', "against" and βίος ''bios'', "life"—is broadly used to refer to any substance used against microbes, but in the usual medical usage, antibiotics (such as penicillin) are those produced naturally (by one microorgani ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tabtoxin
Tabtoxin, also known as wildfire toxin, is a simple monobactam phytotoxin produced by ''Pseudomonas syringae''. It is the precursor to the antibiotic tabtoxinine β-lactam (TBL). It is produced by: * Pseudomonas syringae pv. tabaci, the causal agent of the wildfire of tobacco. * P. syringae pv. coronafaciens * P. syringae pv. garcae * P. syringae BR2, causes a disease of bean (Phaseolus vulgaris) similar to tobacco wildfire. This organism is closely related to P. syringae pv. tabaci but cannot be classified in the pathovar tabaci because it is not pathogenic on tobacco. Tabtoxin is a dipeptide precursor to the biologically active form of TBL, differing by having an extra threonine attached by a peptide bond to the C terminus. Tabtoxin is required by BR2(R) for both chlorosis and lesion formation on bean. All mutations that affected tabtoxin production, whether spontaneous deletion or transposon induced, also affected lesion formation, and in all cases, restoration of tabtoxin produ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beta-lactam Antibiotic
β-lactam antibiotics (beta-lactam antibiotics) are antibiotics that contain a beta-lactam ring in their chemical structure. This includes penicillin derivatives ( penams), cephalosporins and cephamycins ( cephems), monobactams, carbapenems and carbacephems. Most β-lactam antibiotics work by inhibiting cell wall biosynthesis in the bacterial organism and are the most widely used group of antibiotics. Until 2003, when measured by sales, more than half of all commercially available antibiotics in use were β-lactam compounds. The first β-lactam antibiotic discovered, penicillin, was isolated from a strain of '' Penicillium rubens'' (named as ''Penicillium notatum'' at the time). Bacteria often develop resistance to β-lactam antibiotics by synthesizing a β-lactamase, an enzyme that attacks the β-lactam ring. To overcome this resistance, β-lactam antibiotics can be given with β-lactamase inhibitors such as clavulanic acid. Medical use β-lactam antibiotics are indicated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Penicillin-binding Proteins
Penicillin-binding proteins (PBPs) are a group of proteins that are characterized by their affinity for and binding of penicillin. They are a normal constituent of many bacteria; the name just reflects the way by which the protein was discovered. All β-lactam antibiotics (except for tabtoxinine-β-lactam, which inhibits glutamine synthetase) bind to PBPs, which are essential for bacterial cell wall synthesis. PBPs are members of a subgroup of enzymes called transpeptidases. Specifically, PBPs are DD-transpeptidases. Diversity There are a large number of PBPs, usually several in each organism, and they are found as both membrane-bound and cytoplasmic proteins. For example, Spratt (1977) reports that six different PBPs are routinely detected in all strains of '' E. coli'' ranging in molecular weight from 40,000 to 91,000. The different PBPs occur in different numbers per cell and have varied affinities for penicillin. The PBPs are usually broadly classified into high-molecula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glutamine Synthetase
Glutamine synthetase (GS) () is an enzyme that plays an essential role in the metabolism of nitrogen by catalyzing the condensation of glutamate and ammonia to form glutamine: Glutamate + ATP + NH3 → Glutamine + ADP + phosphate Glutamine synthetase uses ammonia produced by nitrate reduction, amino acid degradation, and photorespiration. The amide group of glutamate is a nitrogen source for the synthesis of glutamine pathway metabolites. Other reactions may take place via GS. Competition between ammonium ion and water, their binding affinities, and the concentration of ammonium ion, influences glutamine synthesis and glutamine hydrolysis. Glutamine is formed if an ammonium ion attacks the acyl-phosphate intermediate, while glutamate is remade if water attacks the intermediate. Ammonium ion binds more strongly than water to GS due to electrostatic forces between a cation and a negatively charged pocket. Another possible reaction is upon NH2OH binding to GS, rather ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lactams
A lactam is a cyclic amide, formally derived from an amino alkanoic acid. The term is a portmanteau of the words ''lactone'' + ''amide''. Nomenclature Greek prefixes in alphabetical order indicate ring size: * α-Lactam (3-atom rings) * β-Lactam (4-atom rings) * γ-Lactam (5-atom rings) * δ-Lactam (6-atom rings) * ε-Lactam (7-atom rings) This ring-size nomenclature stems from the fact that a hydrolyzed α-Lactam leads to an α-amino acid and a β-Lactam to a β-amino acid, ''etc''. Synthesis General synthetic methods exist for the organic synthesis of lactams. Beckmann rearrangement Lactams form by the acid-catalyzed rearrangement of oximes in the Beckmann rearrangement. Schmidt reaction Lactams form from cyclic ketones and hydrazoic acid in the Schmidt reaction. Cyclization of amino acids Lactams can be formed from cyclisation of amino acids via the coupling between an amine and a carboxylic acid within the same molecule. Lactamization is most efficient in thi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
