Alteration in the status of glutathione transferase of the water snail, Bulinus globosus, during aestivation and recovery

Abstract

Th e varying status of glutathione transferases (GSTs) in water snail, Bulinus globosus , an intermediate host of disease-causing Schistosoma haematobium (Bilharz 1852) has been investigated. Th e expression of GST isoenzymes in the water snail appears seasonal with about three isoenzymes appearing during raining season, when the organism is active, which may reduce to a single peak of one isoenzyme during aestivation, when the organism is inactive. GST isoenzyme is present in high concentration in all the tissues investigated namely: haemolymph, foot muscle and hepatopancreas with specifi c activities of 0.006 ± 0.002, 0.45 ± 0.021 and 1.33 ± 0.103 units/mg protein respectively for 1-chloro-2,4-dinitrobenzene (CDNB) as substrate. With this substrate, the specifi c activity of GST from the hepatopancreas appears higher than the specifi c activities that have been previously reported for GSTs from molluscs. Partial purifi cation of the isoenzymes using Tris acrylic acid-based resins enabled us to observe that GST appears to be the major protein in the hepatopancreas of this organism. We also found indications for the presence of an endogenous GST inhibitor in the cytosol, whose function is yet unknown. All the traditional GST inhibitors such as cibacron blue, hematin, bromosulfophthalein and S-hexylglutathione were able to inhibit the isoenzymes eff ectively, with cibacron blue being the most potent. Th e isoenzymes however have narrow substrate specifi city. We conclude that diff erent isoenzymes of GST are expressed in the same class of molluscs, even when they belong to the same genus or species, and that the expression may depend on whether the snails are on aestivation or not.