Abstract
Hemoglobin is a member of hemoprotein superfamily whose main role is to transport O2 in vertebrate organisms. It has also two known promiscuous enzymatic activities, namely peroxidase and oxygenase. Here we show for the first time that bovine hemoglobin also presents a catalase-like activity characterized by a Vmax of 344 µM/min, a KM of 24 mM and a kcat equal to 115 min-1. For high anthracene and hemoglobin concentrations and low hydrogen peroxide concentrations, this activity inhibits the expected oxidation of anthracene, which occurs through a peroxidase-like mechanism. Anthracene belongs to the polycyclic aromatic hydrocarbons family whose members are carcinogenic and persistent pollutants found in industrial waste waters. Our results show that anthracene oxidation by hemoglobine and hydrogen peroxide follows a typical bi-bi ping-pong mechanism with a Vmax equal to 0.250 µM/min, KM(H2O2) of 80 µM, KM(ANT) of 1.1 µM and kcat of 0.17 min-1. The oxidation of anthracene is shown to be pseudo-catalytic because an excess of hemoglobin and hydrogen peroxide is required to make PAH completely disappear. Thus bovine hemoglobin presents, in different degrees, all the catalytic activities of the hemoprotein group which makes it a very interesting protein for biotechnological processes and with which one can study structure-activity relationships.