An energy-dependent polymerization-depolymerization phenomenon in the beta-glucosidase (beta-D-glucoside glucohydrolase, EC 188.8.131.52) in the gut contents of the giant African snail Achatina achatina has been observed. The formation of the octamer, tetramer and dimer from the monomer (mol. wt. approx. 41 000) and vice versa are catalysed by proteins in the present gut contents.