Interaction of chromium(III) or chromium(VI) with catalase and its effect on the structure and function of catalase: An in vitro study

•Interaction mechanisms of Cr(III) or Cr(VI) with CAT were different.•Cr(VI) showed a stronger interaction strength with CAT than Cr(III).•Cr(III) or Cr(VI) altered the structure of CAT to different degrees.•The response of CAT activity to Cr(III) or Cr(VI) depends on their concentrations.

Heavy metal chromium (Cr) poses a severe health risk to humans via food chain contamination. In this study, the interactions of either trivalent chromium (Cr(III)) or hexavalent chromium (Cr(VI)) with catalase (CAT) were investigated via multi-spectroscopic studies and computational simulations. The fluorescence analysis showed that Cr(III) and Cr(VI) quenched the fluorescence of CAT through a dynamic and a static quenching mechanism, respectively. The binding constant of Cr(VI) with CAT was 3.44 × 104 l mol−1 at 298 K. Other detailed binding characterizations of the Cr(VI)-CAT complex were also obtained using spectra analysis and molecular docking. Synchronous fluorescence, UV-vis and circular dichroism (CD) spectral studies showed that either Cr(III) or Cr(VI) induced conformational changes of CAT, but the degree of influence was different. The response of CAT activity to Cr(III) or Cr(VI) was found to be variable depending on their valence states and concentrations.