Crystallographic B factor of critical residues at enzyme active site

Thirty-seven sets of crystallographic enzyme data were selected from Protein Data Bank (PDB, 1995) . The average temperature factors ( B) of the critical residues at the active site and the whole molecule of those enzymes were calculated respectively. The statistical results showed that the critical residues at the active site of most of the enzymes had lower B factors than did the whole molecules, indicating that in the crystalline state the critical residues at the active site of the natural enzymes possess more stable conformation than do the whole molecules. The flexibility of the active site during the unfolding by denaturing was also discussed.