Biosynthesis of polymyxin E III. Total synthesis of polymyxin E by a cell-free enzyme system

Polymyxin E, an antimicrobial branched cyclic decapeptide, was synthesized by an enzyme fraction partially purified from crude extracts of the producing organism, $\text{Aerobacillus}\text{polyaerogenes}$. For the synthesis, three constituent amino acids (L-2,4-diaminobutyric acid, L-leucine, and L-threonine), ATP, Mg²⁺ and an acylating system consisting of octanoyl CoA and an ammonium sulfate fraction of cell extracts are required.