Two alternative specific and very sensitive methods for determination of vinyl epoxide synthetase activity in liver microsomes are described. Trichloroethylene, which is used as a substrate, is converted into trichloroethylene oxide by a hepatic epoxide synthetase. Chloral hydrate, the final rearrangement product of trichloroethylene oxide, is evaluated by electron capture gas chromatography, either after derivatization with pentafluorophenyl-hydrazine or after its conversion into chloroform under alcaline conditions. The kinetic parameters of the epoxidative reaction have been determined on rat hepatic microsomal suspensions.
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Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States. Electronic address:
Gamma-glutamyl carboxylase (GGCX), a polytopic membrane protein found in the endoplasmic reticulum, catalyzes the posttranslational modification of a variety of vitamin K-dependent (VKD) proteins to their functional forms. GGCX uses the free energy from the oxygenation of reduced vitamin K to remove the proton from the glutamate residue to drive VKD carboxylation. During the process of carboxylation, reduced vitamin K is oxidized to vitamin K epoxide.
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