Purification and characterization of glutathione transferase from the giant African snail, Archachatina marginata

Abstract

1. 1. Glutathione- S-transferase has been purified from the hepatopancreas of Archachatina marginata to homogeneity. 2. 2. The enzyme was found to be a dimer with a molecular weight of 44,000. The subunits sizes were 22,500 and 23,500 respectively. The isoelectric points of the enzyme were 8.35, 7.95 and 4. The enzyme was most stable at temperature below 40°C. Upon denaturation by 4 M urea, only 56% of the activity could be recovered. 3. 3. The K ms for glutathione and 1-chloro-2,4-dinitrobenze (CDNB) were 0.23 mM and 0.4 mM respectively. The specific activity of the enzyme with CDNB and p-nitrophylacetate as substrates were 47 μmol/mg and 38 μmol/mg respectively. 4. 4. Inhibition studies showed that S-hexylglutathione, Rose Bengal, iodoacetamide, sodium azide and Procion Blue H-B were good inhibitors with i 50 values ranging from 18.5 μM to 299 mM. 5. 5. The amino acid composition showed that the enzyme had a relatively high content of hydrophobic and acidic amino acid residues. The peptide maps of the tryptic digests of the native and performic acid-oxidised enzyme indicated that there might be about two disulphide bridges per molecule of the enzyme.