Chitosan was readily depolymerized by a wheat germ lipase preparation, from approximately 700,000 to 13,000 D, as shown by the viscosity decrease of its lactate solutions, gel permeation chromatography, electrophoresis, and titration of the reducing sugars. Typically, the viscosity was lowered to 35% of the initial value upon 10-min contact with lipase at 25 degrees C. Measurements taken in the lipase concentration range 4.5 10(-3) to 9 10(-1) g/l(-1) showed a logarithmic dependence of the initial velocity on the enzyme concentration. N-Carboxymethyl chitosan was an even better substrate, with the initial velocity over double that for chitosan. This work indicates for the first time the possible involvement of lipases in the dietary significance of chitosans, and in the resorption of chitosan-based medical items.