Xenobiotics

• Multi-Drug Resistance in Cancer - Role of ABC Transporter Proteins
• Cytochrome P450s (CYPs)
• Cytochrome-P450 Reductase
• Cytochrome b5
• Sulfotransferase (SULTs)
• Glutathione Transferases
• UDP-glycosyltransferase (UGT/GLUCs)
• Cytochrome P450 Fluorescent Detection Kits
• Substrates
• Inhibitors

The hepatic microsomal cytochrome P450s are members of a superfamily of monoxygenases that catalyze the oxidative metabolism of xenobiotics, the initial step in the biotransformation and elimination of a wide variety of drugs and environmental pollutants. P450s are located primarily in the endoplasmic reticulum of liver tissue. Until now the difficulty of isolating and reconstituting native enzymes from human tissue has hampered their use for studies with well-defined in vitro drug metabolism systems.

• Isozyme identification
• Determination of kinetic parameters for substrates and inhibitors
• Isolation and synthesis of rare and novel metabolites
• Stereo- and/or regio-specific hydroxylation reactions
• High-throughput in vitro screening

Hepatic microsomal cytochrome P450, human recombinant, was expressed in over producing E. coli.

Hepatic microsomal cytochrome P450 2B4 from rabbit liver was induced with phenobarbital.

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Cytochrome-P450 reductase transfers electrons from NADPH to the various isoforms of cytochrome P450. It is a membrane-bound flavoprotein containing one mole each of FAD and FMN. Sigma offers two product options. Sigma's human Cytochrome-P450 reductase is produced from insect cells infected with baculovirus containing the cDNA for human P450 reductase.Sigma's nonrecombinant version is isolated from rabbit liver induced with phenobarbital.

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Cytochrome b5 is a membrane-bound hemoprotein that enhances the catalytic efficiency of some P450 isoforms. Sigma's human cytochrome b5 is overexpressed in E. coli and purified to homogeneity.

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Five allelic variants of sulfotransferase enzymes are offered for sudies involving drug disposition research. Sigma's highly active cytosolic extracts are produced from insect cells that are infected with a baculovirus containing a cDNA for human sulfotransferases.

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Glutathione transferases (GSTs) catalyze the formation of thioether conjugates between glutathione and xenobiotic compounds. Their major biological function is believed to be defense against electrophilic chemical species, many of which are formed by cellular oxidative reactions catalyzed by cytochrome P450 and other oxidases. Sigma's recombinant human GSTs are over-expressed in E. coli and purified by affinity chromatography.

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Examining the glucuronidation reactions catalyzed by the human UDP-glycosyltransferase (UGT) family of enzymes is essential when investigating the metabolic fate of any new drug, therapeutic agent, or chemical present in the environment. Sigma's human UDP-glycosyltransferases are produced as a microsomal fractions of Sf-9 insect cells infected with a baculovirus strain containing cDNA for a specific human UGT.

Cytochrome P450 Fluorescent Detection Kits. With these kits, you can extract samples and assay them for either cytochrome P450 2B4 or P450 1A1/2 activity.Kits contain sufficient reagents for extraction of up to 7.5 g of tissue and up to 50 assays. Ethoxyresorufin and methoxyresorufin are supplied as substrates.

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Substrates

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Inhibitors

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