Differential response of catalase to As (III) and As (V): Potential molecular mechanism under valence effect

Arsenic (As) is the most prolific contaminant in food, triggering arseniasis primarily via contaminated rice and drinking contaminated water. However, toxicological data for arsenite (As (III)) and arsenate (As (V)) on antioxidant enzyme catalase (CAT) at molecular level is shortage. The interaction mechanism of As (III) and As (V) with CAT was investigated using enzyme activity detection, multi-spectroscopic techniques, isothermal titration calorimetry and computational simulations. Results indicated As (III) and As (V) induced protein skeleton relaxation, secondary structure transformation, fluorescence sensitization and particle alteration of CAT, particularly As (III). Moreover, As (III)/As (V) bound to CAT through hydrogen bonding and hydrophobic. As (III) and As (V) contacted with core residues His 74, Asn 147 and His A74, Trp A357, respectively, thereby inhibiting CAT activity. Overall, As (III) is more aggressive against the structure and physiological function of CAT than As (V). Our findings enhance the understanding of health risk related to dietary As exposure.