Vanadium Chloroperoxidase as a Catalyst for Hydrogen Peroxide Disproportionation to Singlet Oxygen in Mildly Acidic Aqueous Environment

摘要

Chemilumineacence studies show that the enzyme vanadium chloroperoxidase from the fungus Curvularia inaequalis is a highly effecient catalyst for the production of singlet oxygen from hydrogen peroxide in a mildly acidic aqueous enviroment with a maximum turnover frequency of 100s~-1 with respect to H_2O_2 consumption.The enzyme studied here can be regarded as a supplementray latalyst to inorganic molybdate which operates in basic aqueous media The znzyme is very stable against singlet oxygen in contrast to heme-containing peroxid ases which due to inactivation by singlet oxygen only produce a short burst presumably by oxidation of the labile cofactor The vanadium chloroperoxidase was compared with vanadium bromoperoxidase from the seaweed Ascophyllum modosum and was found to be even more stable it is stable towards a continuors flow of inglet oxygen for at least 1 hour and also it is not inactivated by 500 mM H_2O_2 An imporant difference with vanadium bromoperoxidase is that the vanadium chloroperoxidase is able to effectively use chloride as a cocatalyst (20 s~-1) instead of bromide.This offers an important advantage from an application point of view using chloride no side products are observed when the chemical trap anthracene-9,10-bis(ethanesulphonate) is fully con-verted by singlet oxygen into its corresponding endoperoxide By contrast when bromide is used 20% side product is formed.During the conversion the enzyme remains full stable for 25,000 turnovers.