Biomaterial Database

Continuous spectrophotometric assays for cytosolic epoxide hydrolase. 1988

R N Wixtrom, and B D Hammock

Department of Entomology, University of California, Davis 95616.

Two convenient and sensitive continuous spectrophotometric assays for cytosolic epoxide hydrolase are described. The assays are based on the differences in the ultraviolet spectra of the epoxide substrates and their diol products. The hydrolysis of 1,2-epoxy-1-(p-nitrophenyl)pentane (ENP5) is accompanied by a decrease in absorbance at 302 nm, while the hydration of 1,2-epoxy-1-(2-quinolyl)pentane (EQU5) produces an increase in absorbance at 315.5 nm. The Km, Vmax values for ENP5 and EQU5 with purified mouse liver cytosolic epoxide hydrolase were 1.7 microM, 11,700 nmol/min/mg and 25 microM, 8300 nmol/min/mg, respectively. Both substrates are hydrolyzed significantly faster than trans-stilbene oxide, which is currently the most commonly used substrate for measuring cytosolic epoxide hydrolase activity. No spontaneous hydrolysis of the substrates is detectable under normal assay conditions. The assays are applicable to whole tissue homogenates as well as purified enzyme preparations. p-Nitrostyrene oxide and p-nitrophenyl glycidyl ether were also examined and found to be very poor substrates for cytosolic epoxide hydrolase from mouse liver.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008099	Liver	A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.	Livers
D008297	Male		Males
D009578	Nitrobenzenes	BENZENE derivatives carrying nitro group substituents.
D011804	Quinolines
D003600	Cytosol	Intracellular fluid from the cytoplasm after removal of ORGANELLES and other insoluble cytoplasmic components.	Cytosols
D004851	Epoxide Hydrolases	Enzymes that catalyze reversibly the formation of an epoxide or arene oxide from a glycol or aromatic diol, respectively.	Epoxide Hydrase,Epoxide Hydrases,Epoxide Hydratase,Epoxide Hydratases,Epoxide Hydrolase,9,10-Epoxypalmitic Acid Hydrase,Microsomal Epoxide Hydrolase,Styrene Epoxide Hydrolase,9,10 Epoxypalmitic Acid Hydrase,Acid Hydrase, 9,10-Epoxypalmitic,Epoxide Hydrolase, Microsomal,Epoxide Hydrolase, Styrene,Hydrase, 9,10-Epoxypalmitic Acid,Hydrase, Epoxide,Hydrases, Epoxide,Hydratase, Epoxide,Hydratases, Epoxide,Hydrolase, Epoxide,Hydrolase, Microsomal Epoxide,Hydrolase, Styrene Epoxide,Hydrolases, Epoxide
D004852	Epoxy Compounds	Organic compounds that include a cyclic ether with three ring atoms in their structure. They are commonly used as precursors for POLYMERS such as EPOXY RESINS.	Epoxide,Epoxides,Epoxy Compound,Oxiranes,Compound, Epoxy,Compounds, Epoxy
D006863	Hydrogen-Ion Concentration	The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH	pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D006868	Hydrolysis	The process of cleaving a chemical compound by the addition of a molecule of water.