Improving the activity and thermal stability of trypsin by the rational design

The direct evolution combined with the rational design was performed to improve the catalytic properties of the trypsin. ET mutation trypsin included the mutated sites of S40P, G86P, N192Y and Q194L. The optimum of ET mutation trypsin activity was 80.0 ℃. The half life of wild type trypsin and ET mutant trypsin was 420.1 min or 630.1 min respectively. The activity of ET mutation trypsin increased from 3156.95 U/mg to 3951.68 U/mg. Km of ET mutation trypsin was reduced from 26.2 mM to 25.6 mM. Kcat of ET mutation trypsin increased from 3.309/s to 3.312/s. 150–200 amino acids residues of ET mutation trypsin had the higher hydrophobicity. Based on the molecular docking results, the hydrogen bond between the 48th histidine residue and the substrate became shorter after the ET mutation. The evolution increased remarkably the activity and thermal stability of the trypsin.