All of the following enzymes may contribute in generating free oxygen radicals within neutrophils for killing intracellular bacteria, except:
Superoxide Dismutase
Fenton's reaction
NADPH oxidase
Glutathione Peroxidase
Glutathione peroxidase is an enzyme which works as an antioxidant. It catalyses the reaction in which H2O2 is conveed into water. So it does not generate free radicals. Ref: Robbins pathologic basis of disease 6th edn/page 12,13,14.