Sodium dodecyl sulphate dependent NADPH oxidation: an alternative method for assaying NADPH-oxidase in a cell-free system

In assaying NADPH-oxidase activities using macrophage-derived cell-free systems, sodium dodecyl sulphate dependent NADPH oxidation rates were found to correlate strongly with superoxide-dismutase inhibitable cytochrome-c reduction rates. Optimum sodium dodecyl sulphate concentration was in the range 95-110 microM. A theoretical function for the activation and deactivation of NADPH-oxidase by sodium dodecyl sulphate is suggested. This function may serve to estimate the real Vmax of the enzyme and the number of detergent molecules required for the full activation of the enzymatic complex.