Tyrothricin is a large cyclic polypeptide antibiotic isolated from Brevibacillus brevis in 1939. The name Tyrothricin is derived from Tyrothrix, a name first used by Duclaux to designate sporulating aerobic bacteria. Tyrothricin is composed of a mixture of tyrocidine and gramicidin, which are short polypeptides with antimicrobial activity. The complex is a mixture comprised of 60% Tyrocidine and 40% gramicidins. Tyrocidine is composed of non-ribosomally produced cationic cyclic decapeptides (the six predominant tyrocidines are TrcA/A1, TrcB/B1, TrcC/C1) and adopts a β-sheet structure with both L and D amino acids. Gramicidins adopt similar B-sheet structures, and are neutral linear, with valine-Gramicidin A often the major component. Tyrothricin is soluble in alcohol and insoluble in water.
|Mechanism of Action||Tyrothricin targets and inserts into the Gram-positive membrane where it disrupts normal permeability leading to cell death, but the exact mechanism is unclear. Tyrocidines appear to act as reversible inhibitors of acetylcholinesterase and β-galactosidase.|
|Spectrum||Tyrothricin is effective against Gram-positive bacteria, fungi, and some viruses. It has bacteriocidal activity. The antifungal activity is dictated by the primary sequence of the tyrocidine.|
|Microbiology Applications||An interesting property of antimicrobial peptides (AMPs) is that even in vitro, it is nearly impossible to induce resistance. However, there are toxicity concerns, as the components of Tyrothricin can disrupt the eukaryotic cell membranes at high concentrations resulting in toxicity.|
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