GLUTATHIONE-S-TRANSFERASE ACTIVITY IN THE DIGESTIVE GLAND OF THE POND SNAIL, LYMNAEA-STAGNALIS

1. Cytosolic as well as microsomal GST activity of the digestive gland of Lymnaea stagnalis has been examined. 2. The concentration of GSH in the cytosolic fraction (170,000 g supernatant) of snail digestive gland was 135 +/- 4 nmol GSH per g tissue. 3. The optimum temperature (30-degrees-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 cytosolic 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-mu-mol CDNB, the concentration of mercapturic acid of CDNB was determined in water samples (containing excretion products): 0.53 +/- 0.03-mu-M 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.