Biological protection by superoxide dismutase

Diol dehydrase from $\text{Aerobacter aerogenes}$ was dissociated into two different protein components or subunits, designated Components F and S, by chromatography on DEAE-cellulose. Neither component alone possessed any appreciable catalytic activity. Diol dehydrase activity was restored when the two components were combined. Both components were also required for inactivation of coenzyme B₁₂ by oxygen when incubation was carried out in the absence of substrate aerobically. The more acidic component, Component S, was a sulfhydryl protein sensitive to an alkylating agent, iodoacetamide. Coenzyme B₁₂ was not bound by the individual components, F or S, both of which were necessary for the cobamide binding. The presence of substrate, 1,2-propanediol, in eluting buffer retarded the dissociation of the enzyme.