A kinetic study of gelatin-catalyzed hydrolysis of p-nitrophenyl acetate has been carried out in the 246-345 K interval. The observed initial reaction rate in frozen samples has been found to correlate with the content of nonfreezing water at the temperature of the experiment and with the composition of the frozen solution. The observed increase in effective activation energy of hydrolysis upon freezing is explained by an increasingly important role of intermolecular interactions in the kinetics of the reactions taking place with the participation of macromolecules in water-polymer systems that are capable of cryostructurization.