Tannins are present in many plant foods. Tannase (EC 188.8.131.52) catalyses hydrolysis of ester bonds in hydrolysable gallotannins releasing glucose and gallic acid. Enzyme was produced by Penicillium chrysogenum cultured in Czapek-Dox medium containing tannic acid. The tannic acid was used as a substrate in the enzymatic reactions. The product inhibits the enzymatic reaction. It was determined that inhibition was of the competitive type. The mathematical model (Eg. 7) and kinetic constancy describing the process were determined: KM=0,5310-4[mol/dm3], RM=1,2610-3 [mol/dm3 min], KP=2,0410-4 [mol/dm3]. The results obtained from the model well agree with those obtained experimentally.