Tyrocidine
Tyrocidine is a cyclic decapeptide antibiotic that is produced by Bacillus brevis, a Gram-positive aerobic spore-forming bacillus commonly found in soil, air, water, and decaying matter. Tyrocidine is in fact a mixture of four cyclic decapeptides, tyrocidines A, B, C, and D. Tyrocidine is a constituent of tyrothricin, a mixture of polypeptide antibiotics.
Contents:
1. History
2. Structure
3. Biosynthesis
4. Mechanism of action
5. Clinical use
History
Tyrocidine is a constituent of tyrothricin, which was originally isolated by Rene Dubos in 1939, and was the first commercially produced antibiotic.
Structure
Biosynthesis
The cyclic decapeptide antibiotic tyrocidine is produced by Bacillus brevis on an enzyme complex comprising three peptide synthetases, TycA, TycB, and TycC (tyrocidine synthetases 1, 2, and 3), via the nonribosomal pathway. Nonribosomal pathways are characterized by substrates that are not restricted to the 20 proteinogenic amino acids; that is to say, the amino acids that are found in proteins and that are coded for in the standard genetic code. Products synthesized using this pathway can incorporate nonproteinogenic amino acids, such as hydroxy-, D-, and N-methylated amino acids.
1. Amino acids are first activated by conversion into AMP esters, which then bind to the enzyme through thioester linkages.
2.
Mechanism of action
Tyrocidine kills bacteria by interacting with their cytoplasmic membrane and causing leakage of their intracellular content. It also affects intracellular membranes such as those of mitochondria.
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