CAT and chronic kidney disease: Antioxidant enzyme activity was significantly reduced in the CKD group, with superoxide dismutase measuring 1.9 ± 0.6 U/mL compared with 3.8 ± 0.9 U/mL in controls, and catalase measuring 28.5 ± 6.7 kU/L compared with 46.2 ± 8.1 kU/L, respectively (p < 0.001 for both).