Thermal stability of the cellulose synthase complex of Acetobacter xylinum

The thermal stability of the cellulose synthase complex of Acetobacter xylinum has been analyzed in terms of enzyme activity loss as well as detection of its two major components (83kDa and 93kDa polypeptides) in polyacrylamide gels under different electrophoretic sample treatment conditions. The cellulose synthase complex intrinsically is a thermally unstable enzyme and quickly loses its in vitro activity beyond 35°C. The 83 kDa polypeptide has been found to be more labile than the 93 kDa polypeptide. When boiled in lithium dodecyl sulfate (LDS) buffer, the 83 kDa polypeptide is destroyed through peptide hydrolysis while the 93 kDa polypeptide remains uncleaved. The 83 kDa polypeptide is destroyed in LDS buffer at elevated temperatures beyond 55°C. When boiled in the absence of LDS buffer, the 83 kDa polypeptide is completely aggregated, while the 93 kDa polypeptide is only partially aggregated. In the absence of LDS buffer, the complete thermal aggregation of the 83 kDa polypeptide occurs at elevated temperatures beyond 85°C. The aggregation process has been quantitatively analyzed by a newlyintroduced quantitative index, Td (the temperature at which half the quantity of 83kDa polypeptide disappears due to aggregation). The Td determined for the 83kDa polypeptide in the productentrapped fraction is 48°C.