Vitamin K-dependent oxygenase/carboxylase; differential inactivation by sulfhydryl reagents |
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Authors: | L M Canfield |
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Affiliation: | Department of Biochemistry & Biophysics, Texas Agricultural Experiment Station, College Station. |
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Abstract: | Inhibition of vitamin K-dependent carboxylase and oxygenase by sulfhydryl reagents was compared. Formation of vitamin K epoxide and vitamin K-dependent carboxylation are both strongly (greater than 90%) inhibited by l mM p-hydroxy-mercuribenzoate, and this inhibition is reversed by dithiothreitol. Both activities are also effectively inhibited by N-ethylmaleimide (NEM). Preincubation with vitamin K hydroquinone prevents NEM inhibition of epoxide formation but not of carboxylation. These data argue that separate active sites are required to support vitamin K-dependent epoxide formation and carboxylation and that the binding site vitamin K oxygenase contains an active thiol group. |
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