Enzyme action: comparison on soluble and insoluble substrate.

The action of trypsin on gelatin solution is compared with its action on swollen gel microspheres in suspension. Both the solution gelatin and gel spheres, which are readily permeable to the enzyme, follow Michaelis-Menten kinetics. The apparent rate constants for dissociation of the enzyme-substrate complexes to hydrolysis products are essentially the same for both solution gelatin and spheres, an indication that gel structure in this system has a negligible influence on reaction rate once the enzyme forms a complex with the substrate. In contrast, the Michaelis constant for the gel system is greater than that for solutions below the melting point of the gel; this difference disappears as the melting point gel is approached.