Abstract
Inactivation of succinate dehydrogenase by 3-nitropropionate.
Highlights
3-nitropropionate is a suicide inactivator of succinate dehydrogenase and that it acts by nucleophilic addition to N-5 of the covalently bound flavin component of the enzyme
Characteristics of the Inhibition in the Soluble Enzyme-It has been convincingly demonstrated that it is the dianionic form of the aci-nitro group of 3-nitropropionate that inactivates succinate dehydrogenase [3]
Soluble succinate dehydrogenase is quite stable at this pH in anaerobic conditions for the duration of the experiments to be described
Summary
3-nitropropionate is a suicide inactivator of succinate dehydrogenase and that it acts by nucleophilic addition to N-5 of the covalently bound flavin component of the enzyme. Soluble preparations of the enzyme, the inhibition developed slowly, and nearly complete inactivation occurred with a stoichiometric amount of 3-nitropropionate dianion. These facts and the very slow oxidation of 3-nitropropionate by the enzyme (about 0.1% of the rate of succinate oxidation) seem to fit the usual criteria for an active site-directed suicide inhibitor. On denaturation of the enzyme or proteolytic digestion, even in anaerobic conditions, the absorption and fluorescence spectra of the oxidized flavin are observed. This is contrary to the behavior expected of an N-5 alkylated flavin. It is suggested that the inactivation step involves a nucleophilic attack by this essential
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