Stabilization of Creatine Kinase Encapsulated in Silicate Sol−Gel Materials and Unusual Temperature Effects on Its Activity

Abstract

The enzyme creatine kinase (CK) is stabilized by encapsulation in silicate sol−gel monoliths. Its activity is measured as a function of long-term storage time at both room temperature and at elevated temperatures and is compared to that in solution. At room temperature, the activity of the encapsulated enzyme decreases to 50% of its initial value after more than 5 months, whereas in solution it decreases to 50% after 10 days. At 47 °C, the immobilized enzyme retains 50% of its maximum activity after 5 days of constant heating compared to that at 13 h in solution. At 60 °C, the immobilized enzyme retains 50% of its maximum activity after 5 h of heating as compared to that for less than an hour in solution. Surprisingly, a 4-fold increase in activity is observed after short exposures to the elevated temperatures. This increase is explained by structural changes in both the enzyme and the sol−gel matrix. The structural integrity and conformational changes of the encapsulated enzyme are observed by circular d...