1) To investigate the important role of flavinylation (FAD covalently linked to enzyme) in redox potential modulation by using the mutant enzyme mutated at flavinylation site
2) To investigate the important role of catalytic residues by using the mutant enzyme based on the information of crystal structure
3) To elucidate reaction mechanism and the rate-limiting step by using both pre-steady-state kinetic and steady-state kinetic that could be changed by mutant compared with the wild-type enzyme
