Improving the stability and solubility of the ornithine decarboxylase enzyme using rational design

Polyamines play an important role in free radical scavenging. Ornithine decarboxylase is an important enzyme in putrescine biosynthesis. Use of protein engineering to investigate possibility of increasing the solubility and stability of enzyme in drought stress conditions in order to maintain normal enzyme activity, can have a significant effect on improving plant resistance to stress conditions. For this purpose, prediction of thermodynamic stabilization, effects of potential mutations on the thermostability of the enzyme and prediction of dangerous mutations per amino acid were performed using Dezyme software and a systematic search and mutation susceptible points were identified. ۱۰ points selected for mutation and applied individually by Dynamut server. Then destabilizing mutations were ignored and only stabilizing mutations (K۳۴۹R, D۲۳۳F, P۲۵۷Y, P۴۱۲Y) in the form of multiple point mutations was applied. Results of protein stabilization were ۲.۷۲۶ Kcal/mol. Then Examination of amyloid and aggregation formation sites by FoldAmyloid and AGGRESCAN۳D servers showed that the most amino acids involved in formation of amyloid are lysine, valine and (isolucin and tyrosine equally). Mutant enzyme with fewer lysine will be less likely to form amyloid. Also using Prot pi|Protein Tool server, isoelectric point and charge of protein was ۵.۹۰ and -۱۵.۷۹۲. Isoelectric point is far from the cytosolic pH of plant cells (۷.۴), and possibility of enzyme deposition in this medium is low. using Supercharge tool in Rosie server and AVNAPSA method and targeting final protein load on -۱۷, solubility of enzyme increased. resulting Pdb file used in docking process to investigate the binding of enzyme to its cofactor (PLP). Using chimera software, the cofactor structure was optimized. Final docking results on engineered enzyme were obtained as ۱۰ binding conformations with similar amounts of energy, indicating that cofactor binds to enzyme in these conformations and does not interfere with main function of enzyme after mutations

کلیدواژه ها:

Putrescine ، Stress ، Engineered enzyme ، Docking ، Isoelectric point