Alkaline phosphatase (ALP) plays an integral role in the metabolism of liver and development of the skeleton in humans.To date,the interactions between different-duration terahertz (THz) radiation and ALP activities,as well as the influence mechanism are still unclear.In this study,using the para-nitro-phenyl-phosphate (pNPP) method,we detect changes in ALP activities during 40-minute THz radiation (0.1 THz,13 mW/cm2).It is found that the activity of ALP decreases in the first 25 min,and subsequently increases in the later 15 min.Compared with the activity of ALP being heated,the results suggest that short-term terahertz radiation induces a decrease in enzyme activity through the non-thermal mechanism.In order to explore the non-thermal effects of THz radiation on ALP,we focus on the impacts of 0.1 THz radiation for 20 min on the activity of ALP in different concentrations.The results reveal that the activity of ALP decreases significantly after exposure to THz radiation.In addition,it could be deduced from fluorescence,ultraviolet-visible (UV-vis),and THz spectra results that THz radiation has induced changes in ALP structures.Our study unlocks non-thermal interactions between THz radiation and ALP,as well as suggests that THz spectroscopy is a promising technique to distinguish ALP structures.