HEMOGLOBIN, HORSERADISH-PEROXIDASE, AND HEME-BOVINE SERUM-ALBUMIN AS BIOCATALYST FOR THE OXIDATION OF DIBENZOTHIOPHENE

Hemoglobin, horseradish peroxidase, and bovine serum albumin incubated heme-catalyzed the oxidation of dibenzothiophene into sulfoxide in th e presence of hydrogen peroxide. This reaction was carried out in an a queous buffer containing 25% of water-miscible organic solvents. The o bservation of this transient state of hemoproteins during sulfoxidatio n showed heme degradation. None of the compounds usually involved in a classical peroxidative activity mechanism were detected. Furthermore, this activity did not appear to be based on a Fenton-type reaction. T he highest degrees of sulfoxidation were obtained with hemoglobin. Und er the best conditions of reaction, 100% of dibenzothiophene were conv erted into dibenzothiophene sulfoxide by hemoglobin. Heat-denatured he moproteins did keep their sulfoxidation activity. With hemoglobin, a k (cat) of 0.22 min(-1) was determined. Nearly the same values were obta ined with heat-denatured hemoglobin and bovine serum albumin-adsorbed heme. With horseradish peroxidase, only 4% of conversion was attained. This percentage could be slightly increased by using a less pure pero xidase or heat-denatured peroxidase.