Exercise training alters kinetics of antioxidant enzymes in rat tissues.

Michaelis-Menten constant (Km) and maximum velocity (Vmax) of catalase (CAT), glutathione peroxidase (GSH-Px) and glutathione reductase (GR) in various tissues of exercise-trained old rats were compared with the age matched sedentary control. Exercise training increased the maximum velocity (Vmax) for CAT in the brain (350%), liver (33%), lung (34%), muscle (25%) and testes (21%); for GSH-Px (using t-butyl hydroperoxide as a substrate) in the liver (22%), lung (25%), and testes (52%); for GSH-Px (using GSH as a cosubstrate) in the brain (64%) and liver (100%), and for GR in testes (50%). This increase in Vmax indicates the potential activation of these enzymes in the specific tissues. Exercise training differentially altered the affinities of enzyme (Km) for CAT, GSH-Px and GR to their substrates. These studies suggest that exercise training provided a beneficial role by activation of antioxidant enzymes in specific tissues of aged rats. Thus, exercise training aids in coping with oxidative stress in old age.