Author index for volume 179, number 1

Sulfite ion, the hydrated form of SO₂ which is an air pollutant, was found to be an inhibitor of phosphoenolpyruvate carboxylase(s) isolated from corn leaves. The inhibition was partial even in the presence of excess SO₃^2?. It inhibited the enzyme competitively with respect to HCO₃^?, noncompetitively with respect to phosphoenolpyruvate, and uncompetitively with respect to Mg²⁺. The kinetics of inhibition suggest that an alternate pathway is operative in the presence of SO₃^2?. The enzyme(s) were activated by glucose 6-phosphate which affected primarily the affinity of the enzyme for phosphoenolpyruvate. The binding site of glucose 6-phosphate was apparently distinct from the catalytic site of the enzyme since partial destruction of the catalytic site by heat had no effect on the inhibition by SO₃^2?, but glucose 6-phosphate lost its activating effect. The inhibition due to SO₃^2? was relieved by glucose 6-phosphate.