title: Characterization of aspartate transcarbamylase activity from gonads of the soft shell clam, Mya arenaria.
abstract: Aspartate transcarbamylase (ATCase, EC 2.1.3.2) has been shown to be a good index of the reproductive cycle in marine molluscs. However, this enzyme has never been studied in the soft shell clam Mya arenaria. The characteristics of gonadal ATCase of the soft shell clam, Mya arenaria were therefore determined since we need powerful tools to assess the degree of effects of endocrine disruptors in this species at risk. Enzyme kinetic values observed at pH 8.3 were significantly lower than those measured at pH 9.4. The optimal conditions for the enzyme assays were reached in the presence of a 10 mM of substrate concentration and at pH 9.2 for 60 min at 37 degrees C. We have found that the enzyme was heat sensitive, markedly activated by DMSO and DMF, but no effect was observed with ethanol, ATP or CTP. However, clam ATCase activity was partly inhibited by the addition of CuSO(4) and PHMB to the medium, an inhibition that could be attributed to the presence of SH sites in cysteine residues localized in the catalytic site of this enzyme. All these results will be very useful in the near future to study the gametogenetic process of Mya arenaria, since little is known about the factors that control the physiological process of reproduction in this bivalve of ecological and economic importance. Studies of variations of the activity of aspartate transcarbamylase will also be useful as a potential biomarker to evaluate the disruption of gametogenesis in clams exposed to endocrine disruptors in situ.
authors.affiliation: Institut des Sciences de la Mer (ISMER), Université du Québec à Rimouski (UQAR) 310, Allée des Ursulines, Rimouski, G5L 3A1, Québec, Canada.
authors.forename: Olivier Assoi
authors.initials: OA
authors.lastname: Etchian
authors.forename: Jocelyne
authors.initials: J
authors.lastname: Pellerin
mesh_terms: D000818:Animals; D001221:Aspartate Carbamoyltransferase / Q000187:drug effects / Q000378:metabolism*; D049872:Bivalvia / Q000201:enzymology*; D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D005718:Gametogenesis; D006066:Gonads / Q000201:enzymology*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008670:Metals / Q000494:pharmacology; D009711:Nucleotides / Q000494:pharmacology; D012997:Solvents / Q000494:pharmacology
chemical_list: D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D008670:Metals; D009711:Nucleotides; D012997:Solvents; D001221:Aspartate Carbamoyltransferase