Utilization of peroxide and its relevance in oxygen insertion reactions catalyzed by chloroperoxidase

Chloroperoxidase (CPO) catalyzed oxygen insertions are highly enantioselect ive and hence of immense biotechnological potential. A peroxide activation step is required to give rise to the compound I species that catalyzes this chiral reaction. A side reaction, a catalase type peroxide dismutation, is another feature of CPO's versatility. This work systematically investigate s the utilization of different peroxides for the two reactions, i.e. the ca talase type reaction and the oxygen insertion reaction. For the oxygen inse rtion reaction, indene and phenylethyl sulfide were chosen as substrate mod els for epoxidation and sulfoxidation respectively. The results clearly sho w that CPO is stable towards hydrogen peroxide and has a total number of tu rnovers near one million prior to deactivation. The epoxidation reactions t erminate before completion because the enzyme functioning in its catalatic mode quickly removes all of the hydrogen peroxide from the reaction mixture . Sulfoxidation reactions are much faster than epoxidation reactions and th us are better able to compete with the catalase reaction for hydrogen perox ide utilization. A preliminary study towards optimizing the reaction system components for a laboratory scale synthetic epoxidation is reported. (C) 2 001 Published by Elsevier Science B.V.