Stabilization and its Mechanism of Enzyme by Adding Sugar Containing Polymers

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Enzyme is useful in industries such as medicals, foods, fibers. However, enzyme is easy to denaturate by an environmental changes, i.e., temperature, pH and so on. Therefore, the stabilization of enzyme is important in industry. Many studies have been reported on the stabilization of enzymes ; by using stabilizers including saccharides, polyhydric alcohols, and hydrophilic polymer such as poly (ethylene glycol). This study is aimed at investigating the stabilization of enzymes in the presence of sugar containing polymers and attending an insight into the mechanisms of enzyme stabilization. trypsin, L-lactate dehydrogenase, lysozyme, and alpha-amylase were found to be stabilized upon addition of sugar containing polymers. For example, the enzymic activity of native trypsin decrease to 40% by only standing at 30"*"C for 6hr, however, that increased to 60% in the presence of sugar containing polymers. The influence of the sugar containing copolymer, especially comonomer content, on enzyme stabilization was also discussed. It was found that the enzymic activity further increased to 75% for the trypsin at the above conditions. The mechanism of stabilization could be separated into two ways in this case. Trypsin is so called protease, where trypsin molecule digest each other. The presence of polymer simply prohibits the collision of enzyme molecules. Second, the presence of sugar containing polymer enhanced the enzymic reaction and affinity between enzyme and the substrate, judging from the kinetic parameters, Vmax and Km values. Isothermal microtitlation calorimetry, proton-nuclear magnetic resonance, differential scanning calorimetry, liquid chromatography are also used to investigate the stabilization mechanism.