The Reaction of Fluorescein Mercuric Acetate with Sorbitol Dehydrogenase

Fluorescein mercuric acetate has been shown to be an irreversible inhibitor of calf liver sorbitol dehydrogenase. The interaction between dye and enzyme was followed by inhibition kinetics, absorption spectroscopy, fluorescence spectroscopy, and gel filtration. It was shown that the fluorescent dye reacts with an essential sulfhydryl group on the enzyme, and that the presence of the dye on the enzyme catalyzes a subtle conformational change not observed in the absence of the dye. At the same time, the apparent molecular size of the enzyme-dye complex is indistinguishable from that of the enzyme alone, indicating no major quaternary structural change in the dye-reacted enzyme.