Study on the Stabilization of Enzyme against Heat and Organic Solvents

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We found the following results through this study.1.We found that the roles of two lysyl residues among the common sequence KKR (295K and 296K in inorganic pyrophosphatase from Bacillus subtilis) at the C-terminal region in Family 2 inorganic pyrophosphates (PPase) is the recognition site for the substrate. The_arginyl residue (297R in Bacillus subtilis PPase) is important for maintaining the structure for the pass to let the substrate go through.2.Family 2 PPase is composed of two identical subunits, and each subunits contains 3 molecules of manganese ions.3.B. subtilis PPase subunit is composed from 2 domains (N-domain from 1 to 187 and C-domain from 193 to 323), which are connected by the hinge region composed of 6 amino acid residues. Among these 6 resides, 189G is especially important to keep the enzymatically active structure.4.The prolyl residues on the_surface region of the Family 1 PPase from Thermophilic bacterium PS-3 have no role for the heat stability of enzyme. However, the prolyl residues in the interior region are important for maintain the conformation of enzyme. Especially Pro-72 is very important for maintaining the hexamer, which is absolutely necessary for the heat stabilization of enzyme.5.We succeeded in obtaining the variant F40K, Y57I, P74I, Q80L, S111E fo Family 1 PPase from E. coli, and we are now under investigation of their property to obtain the information about the heat stabilization and organic solvent stabilization.