title: The purification and characterization of glutathione S-transferase from the hepatopancreas of the blue crab, Callinectes sapidus.
abstract: High glutathione S-transferase activity was found in the cytosol of F-cells from the hepatopancreas of the blue crab (Callinectes sapidus). Purification of glutathione S-transferase from hepatopancreas extracts by Sephadex G-200, DEAE-Sephacel, and chromatofocusing resulted in the isolation of two isozymes with isoelectric points of 5.9 and 5.7, as determined by analytical isoelectric focusing. Using 1-chloro-2,4-dinitrobenzene as the substrate the specific activities of the two purified isozymes were 222 and 182 mumol/min/mg, respectively. There was no evidence for basic transferase isozymes. In addition to 1-chloro-2,4-dinitrobenzene the purified glutathione S-transferase isozymes showed activity with p-nitrophenyl acetate, p-nitrobenzyl chloride, bromosulfophthalein, and benzopyrene oxide. Thus, both substitution and addition reactions associated with vertebrate glutathione S-transferase were found in the crab transferases. There was no when ethacrynic acid, methyl iodide, trans-4-phenyl-3-buten-2-one, 1,2-epoxy-(p-nitrophenoxy)propane, cumene hydroperoxide, and t-butyl hydroperoxide were used as substrates. The lack of peroxidase activity is of interest since this activity is commonly found in vertebrate transferase isozymes. The two transferases had a dimeric Mr of 40,800 with similar amino acid compositions and similar kinetic parameters (Vmax, Km, and pH maxima) with 1-chloro-2,4-dinitrobenzene as substrate. The two transferases could be distinguished by their isoelectric points, molecular mass of the monomers (22,300 for GST 1 and 22,300 and 22,400 for GST 2), and different inhibitor mechanisms with hematin and bromosulfophthalein.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D003386:Brachyura / Q000201:enzymology*; D004064:Digestive System / Q000201:enzymology; D005982:Glutathione Transferase / Q000302:isolation & purification* / Q000378:metabolism; D007527:Isoenzymes / Q000302:isolation & purification* / Q000378:metabolism; D007700:Kinetics; D008970:Molecular Weight; D013379:Substrate Specificity
chemical_list: D000596:Amino Acids; D007527:Isoenzymes; D005982:Glutathione Transferase