CAT and vitamin B12 deficiency: To determine whether hypocobalaminemia may affect redox homeostasis in astrocytes, we examined (i) activity of the antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase), (ii) intracellular ROS level, and (iii) reduced thiol status in cells treated with (OH)Cbl(c-lactam) for 27 days.