Temperature dependencies of kinetic and equilibrium parameters of urea hydrolysis catalyzed by native urease and the urease immobilized in a thermosensitive poly-N-isopropylacrylamide gel have been studied. The swelling ratio of the collapsed urease-containing gel is shown to increase in the presence of urea. below a lower critical solution temperature (LCST) of the polymer, the immobilized urease actually has the same catalytic properties as the native enzyme. At temperatures above LCST, the observed catalytic activity of the immobilized enzyme depends chiefly not only on the thermoreversible matrix state, but also on gel water content.