Enzymes epoxidation

The oxidation of naphthalene was one of the earliest examples of an epoxide as an intermediate in aromatic hydroxylation. The epoxide can rearrange nonenzymatically to yield predominantly 1-naph-thol, interact with the enzyme epoxide hydrolase to yield the dihydrodiol, or interact with glutathione S-transferase to yield the glutathione conjugate, which is ultimately metabolized to a mer-capturic add. 

Hydration, in the context of metabolism, is the addition of water to a structure. Epoxides are readily hydrated to diols (see carbamazepine, Table 9.1), the reaction being catalysed by the enzyme epoxide hydrolase. 

Valnoctamide inhibits the enzyme epoxide hydrolase, which is concerned with the metabolism and elimination of carbamazepine and its active epoxide metabolite. ... 

Analogs were prepared through total chemical synthesis in which the unstable epoxide was replaced with a cyclopropyl group (4). This afforded compounds that were not subject to epoxide metabolizing enzymes, epoxide hydrolase, and glutathione transferase. We called these compounds PBT (PaceBioAcTive compounds). The PBT competed with the native compounds in binding to neutrophil... 

Rearrangement of the epoxides to phenols competes with hydration to dihyd-rodiols. The hydration is catalyzed by the microsomal enzyme epoxide hydrolase 362). Dihydrodiols are not formed in the absence of epoxide hydrolase or in the presence of inhibitors of epoxide hydrolase such as l,l,l-trichloro-2,3-propene oxide (TCPO) 138, 203, 417). The dihydrodiols are formed stereospecifically from the 4,5-, 7,8-, and 9,10-epoxides as the (—)-trans isomers 416, 506). 

Epoxides produced as primary metabolites of BaP can, in principle, be converted to glutathione conjugates by glutathione 5-transferases present in the soluble fractions of rat liver homogenates 173). This process has been documented for the 4,5-epoxide (557, 359). However, glutathione conjugates were not formed in appreciable amounts when the 7,8-epoxide and 9,10-epoxide were incubated with rat liver supernatant in the presence of glutathione 482). Epoxides such as the 4,5-epoxide of BaP can also be reconverted to the parent hydrocarbon by the enzyme epoxide reductase, present in the microsomal fraction of rat liver 42, 252). 

This epoxide is further metabolized by the enzyme epoxide hydroxylase to form a trans diol, which undergoes glucuronidation to produce a water-soluble adduct that can be excreted in the urine. 

The epoxide metabolite is believed to exhibit activity similar to that of the parent compound and therefore contributes substantially to the overall therapeutic effects of carbamazepine. This feet must be taken into consideration when a patient is taking other medications. For instance, the antibiotic clarithromycin has been found to inhibit the action of the enzyme epoxide hydroxylase. This causes the concentration of the epoxide to be higher than normal, increasing the potency of carbamazepine. Before a physician prescribes carbamazepine for a patient, potential drug interactions must be taken into account This is an example of one important factor that practicing physicians must consider—specifically, the effect that one drug can have on the potency of another drug. 

What is the mechanism of carcinogenic action of benzo[fl]pyrene An oxidizing enzyme (an oxidase) of the liver converts the hydrocarbon into the oxacyclopropane at C7 and C8. Another enzyme (epoxide hydratase) catalyzes the hydration of the product to the trans diol. 

Cytochrome P450 catalyzes the monooxygenation of arachidonate to form a family of isomeric epoxyeicosatrienoic acids (EETs). These may be, in turn, transformed by the enzyme epoxide hydrolase to the corresponding diols, the dihydroxyeicosatrienoic acids (DHT). In addition, cytochrome P450 can also convert arachidonate into a family of nonchiral HETEs. 

Entzweigende Enzyme, enzymes deramifie Enzyme enzymes Epoxide Epoxydes... 

Enzyme Enzymes Epoxide Epoxides Epoxidiemng Epoxidation EibUchkeh Heritability Erbsenstarken Pea Starches Erdbime Topinambur EidnuB Peanut ErdnnfidI Peanut Oil Erdolchemikalien Oilfield Chemicals Emahmng Food Emte Harvesting Erucasaure Erucic Acid... 

---