The protective effect of natural phenolic compound on the functional and structural responses of inhibited catalase by a common azo food dye

In this research retrieval effects of natural yellow (NY) on the performance of carmoisine (CAR) inhibited bovine liver catalase (BLC) was studied using multispectral and theoretical methods. Kinetic studies showed that CAR inhibited BLC through competitive inhibition (IC₅₀ value of 2.24 × 10⁻⁶ M) while the addition of NY recover the activity of CAR-BLC up to 82% in comparison with the control enzyme. Circular dichroism data revealed that NY can repair the structural changes of BLC, affected by CAR. Furthermore, an equilibrium dialysis study indicated that NY could reduce the stability of the CAR-catalase complex. The surface plasmon resonance (SPR) data analysis indicated a high affinity of NY to BLC compared to CAR and the binding of NY led to a decrease in the affinity of the enzyme to the inhibitor. On the other hand, fluorescence and molecular docking studies showed that the quenching mechanism of BLC by CAR occurs through a static quenching process, and van der Waals forces and hydrogen bonding play a crucial role in the binding of CAR to BLC. MLSD data demonstrated that NY could increase the binding energy of CAR-BLC complex from −7.72 kJ mol⁻¹ to −5.9 kJ mol⁻¹, leading to complex instability and catalase activity salvage.