An activity transition from NADH dehydrogenase to NADH oxidase during protein denaturation

Abstract

A decrease in the specific activity of an enzyme is commonly observed when the enzyme is inappropriately handled or is stored over an extended period. Here, we reported a functional transition of an FMN‐bound diaphorase (FMN–DI) that happened during the long‐term storage process. It was found that FMN–DI did not simply lose its β‐nicotinamide adenine diphosphate (NADH) dehydrogenase activity after a long‐time storage, but obtained a new enzyme activity of NADH oxidase. Further mechanistic studies suggested that the alteration of the binding strength of an FMN cofactor with a DI protein could be responsible for this functional switch of the enzyme.