Gramicidins are often mixed with other antibiotics like tyrocidine and antiseptics. The biosynthesis of tyrocidine involves three enzymes. Later this was shown to be a mix of gramicidin and tyrocidine. Other compounds containing -amino acids are tyrocidine and valinomycin. Tyrothricin was later found to be a mixture of the peptides gramicidin and tyrocidine. The tyrocidine synthetases TycA, TycB, and TycC are encoded on the tyrocidine operon. The antibiotics gramicidin and tyrocidine were first isolated from it. The exact affinity and location of tyrocidine within the phospholipid bilayer is not yet known. Tyrocidine also proved too toxic for systemic usage. Tyrocidine is the major constituent of tyrothricin, which also contains gramicidin.