Glutathione S-transferase

Glutathione S-transferases ( GSTs, including glutathione ) are enzymes which catalyze the binding of glutathione to xenobiotics ( foreign organism organic compounds). The conjugates thus formed may, depending on the organism, are removed by transport out of the cell and excretion or by importing it into vacuoles and subsequent degradation of the metabolism. Glutathione thus plays a central role in the detoxification of organic substances.

The conjugation of glutathione usually happens after activation of the substrate by oxidases by nucleophilic attack of the thiol group of the central cysteine ​​of glutathione. Glutathione transferases have different substrate specificities and by a high number of isoforms (eg, 48 in Arabidopsis thaliana ), a wide range of xenobiotics are detoxified.

Classification

For the following classes are where present, is indicated human genes at the end:

  • MAPEG ( Microsomal GST- I) homotrimers membrane proteins that are highly conserved and present in all living things, with lipoxygenase, and some with leukotriene C4 synthase or glutathione peroxidase activity ( MGST1, MGST2, MGST3 )
  • Kappa: localized in mitochondria and peroxisomes ( GSTK1 )
  • Alpha: make up three percent of the soluble protein of the liver and some are specialized in lipid peroxides ( GSTA1, GSTA2, GSTA3, GSTA4, GSTA5 ). mu ( GSTM1, GSTM2, GSTM3, GSTM4, GSTM5 ). pi ( GSTP1 ). alpha / mu / pi are mammal -specific
  • Sigma: in mammals, but more widespread in invertebrates; DmGSTS1 -1 accounts for about one percent of the soluble protein from in Drosophila melanogaster.
  • Theta: can not use CDNB; Serine is catalytically active, in contrast to tyrosine at alpha / mu / pi ( GSTT1, GSTT2, GSTT4 see UniProt A8MPT4 )
  • Zeta: same maleylacetoacetate isomerase ( EC 5.2.1.2 ), catabolized α -halo carboxylic acids ( GSTZ1 )
  • Omega: in mammals, insects, worms; Cysteine ​​as the active center; show similar to the thioredoxin -like protein thiol transferase and Dehydroascorbatreduktase activity ( GSTO1, GSTO2, see glutathione transferase omega )
  • Beta: bacterial enzymes with active cysteine, involved in catabolism of organic molecules
  • Delta / epsilon: insects specifically with active serine; Function in resistance to insecticides and phytochemicals
  • Helminthic GSTs

The use in biotechnology

Due to the high affinity of glutathione S- transferases, glutathione for these are often used in molecular biology as a protein tag. A fusion protein of the subject to be examined protein and a glutathione -S-transferase can be attached via a glutathione - containing matrix, which can be utilized affinity chromatography to specifically enrich the fusion protein or binding to the fusion protein factors ( pull-down assay).

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