Glutathione-5-transferase activity in the digestive gland of the pond snail, Lymnaea stagnalis

Abstract

1. Cytosolic as well as microsomal GST activity of the digestive gland of Lymnaea siagnalis has been examined. 2. The concentration of GSH in the cytosolic fraction (170,000 bag supernatant) of snail digestive gland was 135 ± 4 nmol GSH per g tissue. 3. The optimum temperature (30°C) and pH (8.2) for GST activity, as well as the kinetic parameters (for GSH and CDNB: V max ca. 1200 and 1000 nmol/mg protein per min, and K m 0.17 and 0.13 mM, respectively) were determined. 4. Enzymatic activity with CDNB as a substrate was 349 ± 74 nmol product/mg eytosolic protein/min; after heating the enzymatic activity was reduced to zero. 5. No active microsomal GST was determined, with and without pretreatment of the microsomal fractions with N-ethylmaleimide. 6. After injection of the snails with 1 μmol CDNB, the concentration of mercapturic acid of CDNB was determined in water samples (containing excretion products): 0.53 ± 0.03 μM mercapturic acid, representing 1.1% (i.e. 11 ± 0.6 nmol) of the administered dose of CDNB was found. 7. It is concluded that the snail possesses a GST phase II detoxification mechanism against electrophilic xenobiotics and electrophilic metabolites.