PHASE II REACTIONS in VS .NET

Generation Code 128A in VS .NET PHASE II REACTIONS
PHASE II REACTIONS
Scanning Code 128 In .NET
Using Barcode Control SDK for .NET Control to generate, create, read, scan barcode image in Visual Studio .NET applications.
and thallium as well as the metalloids, arsenic, selenium, tellurium, and sulfur are methylated. Even the unreactive metals, gold and platinum, are reported as substrates for these reactions.
Make Code128 In .NET
Using Barcode generation for Visual Studio .NET Control to generate, create Code 128 Code Set C image in VS .NET applications.
Glutathione S-Transferases (GSTs) and Mercapturic Acid Formation
Recognize Code 128 Code Set A In .NET Framework
Using Barcode reader for .NET Control to read, scan read, scan image in VS .NET applications.
Although mercapturic acids, the N -acetylcysteine conjugates of xenobiotics, have been known since the early part of the twentieth century, only since the early 1960s has the source of the cysteine moiety (glutathione) and the enzymes required for the formation of these acids been identi ed and characterized. The overall pathway is shown in Figure 7.19. The initial reaction is the conjugation of xenobiotics having electrophilic substituents with glutathione, a reaction catalyzed by one of the various forms of GST. This is followed by transfer of the glutamate by -glutamyltranspeptidase, by loss of glycine through cysteinyl glycinase, and nally by acetylation of the cysteine amino group. The overall sequence, particularly the initial reaction is extremely important in toxicology because, by removing reactive electrophiles, vital nucleophilic groups in macromolecules such as proteins and nucleic acids are protected. The mercapturic acids formed can be excreted either in the bile or in the urine. The GSTs, the family of enzymes that catalyzes the initial step, are widely distributed, being found in essentially all groups of living organisms. Although the bestknown examples have been described from the soluble fraction of mammalian liver, these enzymes have also been described in microsomes. All forms appear to be highly speci c with respect to glutathione but nonspeci c with respect to xenobiotic substrates, although the relative rates for different substrates can vary widely from one form to another. The types of reactions catalyzed include the following: alkyltransferase,
Generate Bar Code In .NET
Using Barcode maker for VS .NET Control to generate, create barcode image in .NET framework applications.
RX + HSCH2CHC(O)NHCH2COOH NHC(O)CH2CH2CH(NH2)COOH glutathione S-transferase RSCH2CHC(O)NHCH2COOH NHC(O)CH2CH2CH(NH2)COOH g- glutamyltranspeptidase RSCH2CH(O)NHCH2COOH + glutamate NH2 cysteinyl glycinase RSCH2CH(NH2)COOH RSCH2CHCOOH NHC(O)CH3 Mercapturic acid + glycine
Decoding Barcode In .NET
Using Barcode scanner for VS .NET Control to read, scan read, scan image in Visual Studio .NET applications.
N-acetyl transferase
Encode Code 128C In Visual C#
Using Barcode creation for VS .NET Control to generate, create Code 128B image in Visual Studio .NET applications.
Figure 7.19 Glutathione transferase reaction and formation of mercapturic acids.
Generate Code128 In .NET
Using Barcode encoder for ASP.NET Control to generate, create Code128 image in ASP.NET applications.
METABOLISM OF TOXICANTS
Code128 Encoder In VB.NET
Using Barcode generator for .NET framework Control to generate, create ANSI/AIM Code 128 image in .NET framework applications.
Cl NO2 + GSH
Print Code-128 In VS .NET
Using Barcode drawer for VS .NET Control to generate, create ANSI/AIM Code 128 image in VS .NET applications.
SG NO2 + HCI
UPC - 13 Printer In .NET Framework
Using Barcode printer for Visual Studio .NET Control to generate, create EAN13 image in .NET applications.
NO2 1-Chloro2,4-dinitrobenzene CH2Cl + Chloromethylbenzene CHCOOC2H5 CHCOOC2H5 Diethylmaleate +
Print UPC A In VS .NET
Using Barcode generator for Visual Studio .NET Control to generate, create UCC - 12 image in VS .NET applications.
CH2SG +
Print USPS Confirm Service Barcode In .NET
Using Barcode encoder for .NET framework Control to generate, create Planet image in .NET framework applications.
CH2COOC2H5 GSH GSCHCOOC2H5
Barcode Printer In C#.NET
Using Barcode generation for .NET framework Control to generate, create bar code image in Visual Studio .NET applications.
SG OCH2CHCH2 O + GSH OCH2CHCH2 OH
Making Bar Code In Visual C#
Using Barcode maker for .NET Control to generate, create bar code image in Visual Studio .NET applications.
NO2 1,2-Epoxy-3(p-nitrophenoxy) propane CH2OSO3H + 1-Naphthalene methyl sulfate
Barcode Printer In Java
Using Barcode creator for Java Control to generate, create barcode image in Java applications.
CH2SG +
Code-128 Scanner In .NET Framework
Using Barcode recognizer for Visual Studio .NET Control to read, scan read, scan image in .NET framework applications.
H2SO4
Make ANSI/AIM Code 39 In Visual Basic .NET
Using Barcode encoder for .NET framework Control to generate, create Code 39 image in .NET applications.
Figure 7.20 Examples of glutathione transferases reactions.
Print Bar Code In .NET
Using Barcode drawer for ASP.NET Control to generate, create barcode image in ASP.NET applications.
aryltransferase, aralkyltransferase, alkenetransferase, and epoxidetransferase. Examples are shown in Figure 7.20. Multiple forms of GST have been demonstrated in the liver of many mammalian species; multiple forms also occur in insects. Most GSTs are soluble dimeric proteins with molecular weights ranging between 45,000 and 50,000 daltons. All forms appear to be nonspeci c with respect to the reaction types described, although the kinetic constants for particular substrates vary from one form to another. They are usually named from their chromatographic behavior. At least two are membrane-bound glutathione transferases, one of which is involved in metabolism of xenobiotics and is designated
Encoding EAN / UCC - 13 In .NET
Using Barcode drawer for ASP.NET Control to generate, create EAN / UCC - 14 image in ASP.NET applications.
PHASE II REACTIONS
Code128 Printer In VB.NET
Using Barcode generator for VS .NET Control to generate, create ANSI/AIM Code 128 image in VS .NET applications.
the microsomal GST. The cytosolic GSTs are divided into six families (historically called classes): the (alpha), (kappa), (mu), (pi), (sigma), and (theta) families. A new system of nomenclature proposes the term GST for the enzyme, preceded by the use of a small roman letter for the species (m for mouse, h for humans, etc.) followed by a capital roman letter for the family (A for , K for , etc.). Subunits are to be designated by arabic numbers, with the two subunits represented with a hyphen between them. For example, hGSTM1-2 designates a heterodimer of the human family mu, which possesses subunits one and two. Glutathione conjugation dramatically increases the water solubility of the metabolites compared to the parent compounds. The metabolites are released from the cell by an active transport system belonging to the multi-drug resistance (mdr) protein. Prior to excretion, the metabolites are usually processed by multiple enzymes to release the substrate conjugated to a mercapturic acid (Figure 7.19). The enzymes involved in this process are -glutamyltranspeptidase, cysteinyl glycinase, and N -acetyl transferase. -Glutamyltranspeptidase is a membrane-bound glycoprotein that has been puri ed from both the liver and kidney of several species. Molecular weights for the kidney enzyme are in the range of 68,000 to 90,000 daltons, and the enzyme appears to consist of two unequal subunits; the different forms appear to differ in the degree of sialalylation. This enzyme, which exhibits wide speci city toward -glutamyl peptides and has a number of acceptor amino acids, catalyzes two types of reactions: Hydrolysis Transpeptidation -Glu-R + H2 O -Glu-R + Acceptor -Glu-R + -Glu-R Glu + HR -Glu-Acceptor + HR -Glu -Glu-R + HR
Aminopeptidases that catalyze the hydrolysis of cysteinyl peptides are known. The membrane-bound aminopeptidases are glycoproteins, usually with molecular weights of about 100,000 daltons. They appear to be metalloproteins, one of the better known being a zinc-containing enzyme. Other enzymes, such as the leucine aminopeptidase, are cytosolic but, at least in this case, are also zinc-containing. The substrate speci city of these enzymes varies but most are relatively nonspeci c. Little is known of the N -acetyltransferase(s) responsible for the acetylation of the S-substituted cysteine. It is found in the microsomes of the kidney and the liver, however, and is speci c for acetyl CoA as the actyl donor. It is distinguished from other N-acetyltransferases by its substrate speci city and subcellular location.