Mechanistic insights into profenofos interactions with antioxidant enzymes in Labeo rohita

Profenofos pesticide (Organophosphate) is one of the most commonly used pesticide products. It has been detected in many freshwater ecosystems and can impact the survival of non-target organisms. Its exposure causes oxidative stress and compromises the ability of fish to regulate its defense mechanisms. While there is significant interest in understanding the effects of profenofos on fish, the exact molecular mechanisms are not yet fully understood. This study is focused on determining the interactions of profenofos with key enzymes of the antioxidant defense system of Labeo rohita (freshwater aquaculture species in South Asia), through structure-based computational approaches. The amino acid sequences of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx), were used to study the secondary and three-dimensional structure modelling, functional annotation, and molecular docking. Structural analyses showed clear differences among the enzymes. CAT was characterized by a predominantly helical fold with moderate beta-strand content, GPx as compact globular structure, and SOD as beta-pleated core. The pathway and functional analyses confirmed that these enzymes have coordinated networks required to maintain homeostasis. The predicted binding pocket indicated that they possess solvent-accessible cavities, but the size and geometry of the cavity significantly differ between them. Molecular docking revealed enzyme-specific binding profiles (CAT: ΔG = -3.68 kcal/mol; SOD: ΔG = -3.11 kcal/mol; GPx: ΔG = -3.30 kcal/mol) with hydrophobic contacts dominating all three complexes. PRODIGY-LIG binding free energy estimation yielded ΔGnoelec values of -5.61, -5.34, and -5.83 kcal/mol for CAT, SOD, and GPx respectively. Key interacting residues identified through docking analysis included Lys168 and His174 for CAT, Cys85 and Ser38 for GPx, and His44 and Glu122 for SOD. The current work provides the detailed molecular examination of the interactions between profenofos and the antioxidant enzymes in L. rohita, supporting previously reported experimental observations of oxidative stress in freshwater fish exposed to organophosphates.