Rapid unfolding of pig pancreas α-amylase: Kinetics, activity and structure evolution

•Kinetics of rapid unfolding of α-amylase was disclosed on the microsecond scale.•Detailed structural changes of α-amylase during the unfolding was described.•Unfolding of α-amylase from pig pancreas by guanidine hydrochloride was studied.•Contribution of H-bond structure of water to protein unfolding was disclosed.•One intermediate existed in the unfolding of pig pancreas α-amylase.