Violacein transformation by peroxidases and oxidases: implications on its biological properties

Abstract

1,3-Dihydro-2H-indol-2-one derivative (violacein) is extracted from Chromobacterium violaceum and presents several biological activities as antibiotic, antitumoral, antichagasic and antioxidant. In order to increase its biological activities and decrease its toxicity, one strategy is to slightly transform the molecules through a specific group transformation. Peroxidases, which are hemoproteins, are known as excellent oxidants producing hydroxylation and ring cleavage. Laccases are phenol oxidases produced by fungi as plants and belong to the oxidase group which complexes copper. This enzyme generates phenolates, quinones and also ring cleavage even in the presence of a mediator as 1-hydroxybenzotriazol (HBT). Lignin peroxidase and manganese peroxidase (LiP/MnP) pool from Phanerochaete chrysosporium, Horseradish peroxidase (HRP-VI) from horseradish, Lactoperoxidase (LPO) from bovine milk and Laccase (Lac) from Trametes versicolor acting on violacein were studied. Kinetics parameters and products distribution indicated a fast and efficient violacein transformation with all of them. HRP-VI acting on violacein was studied in details and spectral evidence indicated that Horseradish peroxidase compound II was formed during the oxidation reaction. Similar behavior with LiP/MnP pool was observed. Laccase, in the presence and absence of mediator (HBT), also showed a rapid violacein transformation. In a more detailed study with the HRP-VI reaction, a hydroxilation in the indol unit and a ring contraction of the pyrrol moiety of violacein molecule occurred.