Activities of antioxidant enzymes in mycelium of fungus Phycomyces blakesleeanus

Abstract

Phycomyces blakesleeanus is a strict aerobic filamentous fungus often used as a model system in studies of physiology, genetics, environmental sensing, and metabolism. As all other aerobic organisms, this fungus faces the toxic effects of oxygen-reactive species, but data about its antioxidative defense systems are scarce. The aim of this research was to examine the activities of three antioxidant enzymes during different phases of growth. The fungus was grown in two ways, in Petri dishes, and on a shaker in Erlenmeyer flasks. The activities of superoxide dismutase (SOD) and peroxidase (POD) were determined spectrophotometrically, while the activity of catalase (CAT) was determined polarographically with a Clark-type oxygen electrode. The highest activities of SOD were noticed in mycelia grown in Erlenmeyer flasks in the stationary phase of growth. In mycelia grown in Petri dishes, the highest activities of POD (0,014U/mg protein) and CAT (20,63 U/mg protein) were noticed in the early exponential phase. The activities of these two enzymes decreased with mycelial growth. In mycelia grown in Erlenmeyer flasks, POD and CAT showed similar behavior, but differences in activities between exponential and stationary phases were smaller and the highest activities were noticed in the mid-exponential to stationary phase of growth (0,011U/mg protein for POD and 17,21U/mg protein for CAT). High activities of these two enzymes indicated increased production of H2O2 and pointed out the importance of this phase for mycelia grown in this way.