Identification and characterization of proteases in the digestive tract of Pomacea canaliculata

MARTÍN S. GODOY & ISRAEL ANÍBAL VEGA

Tucumán

Taller; Biology of Ampullariidae; 2010

The current report is part of a program dealing with the biology of a putative endosymbiont (Castro-Vazquez et al., 2002; Vega et al., 2005; Koch et al., 2006) which is contained within the epithelial cells of the midgut gland (MGG) of adult P. canaliculata. In this context, we have revisited the digestive physiology of this snail because (a) it was previously reported the absence of protease activity in the intestinal content of ampullariids (Meenakshi 1955; Andrews 1964) and (b) the endosymbiont isolated from the MGG had an important intrinsic protease activity (Godoy, 2005) and travel through the intestine to the external environmental. The aim of this work was (1) to examine the changes in specific protease activity (SPA) along the snail’s gut; (2) to estimate by zymography the molecular weight of the proteases present in the different gut regions; (3) to tentatively identify the place of origin of the different proteases found; and (4) to determine the sensitivity of the snail´s proteases to group-specific inhibitors; and (5) to determine their optimal working temperatures. Specific protease activity (mIU/mg of protein) changed significantly (ANOVA, F(2)= 8.49, p=0.001) along the intestine of P. canaliculata. Specific activity in the mid esophagus (crop content) and stomach (gastric vestibule + style sac contents) were of 0.11 ± 0.02 and 0.14 ± 0.02, respectively (mean ± SEM, N=10), but it rose dramatically (6-fold) in the coiled gut (0.86 ± 0.25, N=10: Tukey test, p