Rat liver chemical hepatocarcinogenesis, induced by interrupted feeding of 2-acetylaminofluorene, results in various cellular preneoplastic stages and finally in a hepatoma in about 70 to 90 percent of the rats. The putative precursors of hepatomas, called hyperplastic nodules, appear after 12 weeks of feeding and, after 16 weeks of feeding carcinogen, most of them are persistent. Epoxide hydro...

Membrane-bound and soluble epoxide hydrolase activities in the mononuclear cell fraction from human blood have been characterized using cis- and trans-stilbene oxides as substrates, respectively. Because of the low activities in these cells, it was necessary to modify assay procedures developed for rat and mouse liver in the following ways: (a) the substrates were relatively highly labeled (2 C...

Distribution of epoxide hydrolase activity in subcellular fractions of livers from male Swiss-Webster mice and Sprague-Dawley rats was monitored with trans-B-ethylstyrene oxide, mznsstilbene oxide and benzo[a]pyrene 4,5-oxide following differential centrifugation. With the former two substrates the highest activity was encountered in the cytosolic fraction; however, significant activity was fou...

Epoxides are organic three-membered oxygen compounds that arise from oxidative metabolism of endogenous, as well as xenobiotic compounds via chemical and enzymatic oxidation processes, including the cytochrome P450 monooxygenase system. The resultant epoxides are typically unstable in aqueous environments and chemically reactive. In the case of xenobiotics and certain endogenous substances, epo...

An assay for epoxide hydrolase activity using benzo(a)-pyrene 4,5-oxide as substrate was modified in such a manner that it allowed the estimation of activities in native and in cultivated mitogen-stimulated human lymphocytes. Their specific activities were about 1000-fold lower than those of human or rat liver microsomes. In native lymphocytes of 28 subjects, the specific activities of epoxide ...

OBJECTIVE Microsomal epoxide hydrolase is an important enzyme involved in the metabolism of endogenous and exogenous toxicants. Polymorphic variants of the human epoxide hydrolase gene vary in enzyme activity. We determined whether genetic variability in the gene encoding for microsomal epoxide hydrolase contributes to individual differences in susceptibility to the development of pre-eclampsia...

We have examined the selectivity of rat liver microsomal epoxide hydrolase (EC 3.3.2.3) toward all of the possible positional isomers of benzo-ring diol epoxides and tetrahydroepoxides of benz[a]anthracene, as well as the 1,2-diol 3,4-epoxides of triphenylene. This set includes compounds with no bay region in the vicinity of the benzo-ring, a bay-region diol group, a bay-region epoxide group, a...

Epoxide hydrolases catalyze hydrolytic epoxide ring-opening, most often via formation of a covalent hydroxyalkyl-enzyme intermediate. A mutant of Agrobacterium radiobacter epoxide hydrolase, in which the phenylalanine residue that flanks the invariant catalytic aspartate nucleophile is replaced by a threonine, exhibited inactivation during conversion when the (R)-enantiomer of para-nitrostyrene...

Epoxide hydrolases catalyze hydrolytic epoxide ringopening, most often via formation of a covalent hydroxyalkyl-enzyme intermediate. A mutant of Agrobacterium radiobacter epoxide hydrolase, in which the phenylalanine residue that flanks the invariant catalytic aspartate nucleophile is replaced by a threonine, exhibited inactivation during conversion when the (R)-enantiomer of para-nitrostyrene ...

In Euphorbia lagascae the major fatty acid in triacylglycerol is the epoxidated fatty acid vernolic acid (cis-12-epoxyoctadeca-cis-9-enoic acid). The enzymic reactions occurring during the catabolism of epoxidated fatty acids during germination are not known, but it seems likely that the degradation requires the activity of an epoxide hydrolase. Epoxide hydrolases are a group of functionally re...