Photooxidation in Ternary System Human Serum Albumin-Chlorin e₆-Tryptophan

Summary

Light-induced oxidation reactions in ternary system tryptophan-human serum albumin-chlorin e₆ (Trp-HSA-Cle₆) were investigated. Solutions with different components content were illuminated under red light. Reagent conversion kinetics were estimated by reverse-phase HPLC. Under reaction, photoproducts are formed both free and covalently bound to protein Trp. Their distribution correlates with the initial binding ratio of Trp to albumin. Data obtained were considered in several aspects. (1) The involvement of Trp as a naturally occurring ligand of albumin in photooxidation reactions points out a possibility for targeted in situ generation of physiologically active products of albumin ligands. (2) Production of chemically modified HSA molecules also may have an impact on cell-mediated and vascular responses of photooxidation. (3) Ternary system Trp-HSA-Cle₆ may serve as a prototype of a light-driven oxidation enzyme with the HSA ligand (Trp) as the substrate, Cle₆ as the prosthetic group, and HSA as the apoenzyme.