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CATALASE INACTIVATION FOLLOWING PHOTOSENSITIZATION WITH TETRASULFONATEDMETALLOPHTHALOCYANINES
Author(s) -
Gantchev Tsvetan G.,
Lier Johan E.
Publication year - 1995
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1995.tb05248.x
Subject(s) - chemistry , catalase , phototoxicity , singlet oxygen , photochemistry , radical , heme , absorbance , hydrogen peroxide , polyacrylamide gel electrophoresis , reactive oxygen species , biophysics , biochemistry , oxygen , chromatography , oxidative stress , enzyme , organic chemistry , in vitro , biology
— Catalase (CAT) in solution or incorporated in erythrocytes and K562 leukemic cells is inactivated during photosensitization with tetrasulfonated metallophthalocyantnes (MePcS 4 ). The effect of added scavengers and D 2 0 showed that both singlet oxygen and free radical species are involved in this process. Evidence was found that direct interactions of ground or excited‐stated photosensitizers with CAT are not responsible for CAT inactivation. Specific techniques to probe early damage to the CAT structure involved optical and EPR spectroscopy, HPLC and polyacrylamide gel electrophoresis analyses. Different primary events of photosensitized protein damage included oxidation of cysteine residues as well as other amino acids, as demonstrated by the formation of carbon‐centered free radicals and the loss of absorbance at λ= 275 nm. In parallel, we detected degradation of the CAT heme groups, accompanied by release of Fe(II) ions in solution. These combined phenomena initiate cross‐linkages between CAT subunits and subsequent degradation of the protein with formation of irreversible aggregates in solution. Phthalocyanine‐mediated photoinactivation of cell‐bound CAT results in loss of protection against accumulating H 2 0 2 , providing an additional pathway of phototoxicity.