Snails were anesthetized on ice for 6–8 min. The shells were
carefully removed and the soft tissue isolated at 0 ◦C. The body
soft tissues were washed in distilled water, placed on filter paper
to drain extra fluids, and weighed. One snail per homogenate
was used. Tissues were homogenized in 10V of 20 mM Tris/HCl
buffer, pH 7.5, plus 0.5 mM EDTA. Homogenates were centrifuged
at 11,000 × g for 20 min at 4 ◦C. The resulting supernatants were
used as the enzyme source.