Conversion from Tryptophan Precursor into Violacein Pigments by a Cell-free System fromChromobacterium violaceum

A cell-free system for converting tryptophan precursor into violacein pigments is reported. Crucial factors were the requirements of the reduced nicotinamides as a cofactor and Zn(2+) as a metal ion. Optimal pHs were in the range of 8.5-9.5. The effectiveness of NADH was thirty times lower than that of NADPH at a low concentration of 2mm. The oxygenation mechanism(s) is discussed by using oxygenase inhibitors such as amethopterin, metyrapone, ancymidol, and prohexadione. Metal-chelating agents strongly inhibited the biosynthesis, suggesting that metallo-enzymes are involved in the biosynthesis.