Activation of NADPH-dependent superoxide production in a cell-free system by sodium dodecyl sulfate

Sodium dodecyl sulfate (SDS) elicits the production of superoxide (O₂̄) by a cell-free system represented by sonically disrupted guinea pig peritoneal macrophages. O₂̄ generation requires NADPH and a heat-sensitive cellular component, is proportional to the amount of macrophage protein, and exhibits a pH optimum of 6.5-7. The kinetic parameters of the SDS-stimulated enzyme are: K(m)(±S.E.)=0.0367±0.003 mM NADPH and V(max)(±S.E.)=73.46±9.09 nmol O₂̄/mg of protein/min. O₂̄ production is dependent on the cooperation between a particulate subcellular component sedimentable at 48,000 x g and a cytosolic factor present in the 48.000 x g supernatant. The activity of both components is destroyed by heating at 80 °C. Pretreatment of intact macrophages with phorbol myristate acetate results in the partial removal of the requirement for cytosolic factor; SDS is now capable of activating the isolated 48,000 x g pellet. Among a large number of anionic, cationic, and nonionic detergents tested, only the anionic detergents SDS and sodium dodecyl sulfonate are capable of eliciting O₂̄ production in the cell-free system, SDS being the more potent stimulant. It is proposed that the structural requirements that make these compounds capable of activating the O₂̄ forming NADPH oxidase in a cell-free system are the presence of an anionic polar head and a long hydrophobic alkyl tail. We suggest that sodium salts of long chain unsaturated fatty acids that were found by us to be capable of stimulating O₂̄ production in a cell-free system (Bromberg, Y., and Pick, E. (1984) Cell. Immunol. 88, 213-221) owe their activity to the fact that they function as anionic detergents.