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PHOTOINACTIVATION OF SPINACH NITRATE REDUCTASE SENSITIZED BY FLAVIN MONONUCLEOTIDE. EVIDENCE FOR THE INVOLVEMENT OF SINGLET OXYGEN
Author(s) -
Vargas M. A.,
Mauriño S. G.,
Maldonado J. M.,
Aparicio P. J.
Publication year - 1982
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.1751-1097.1982.tb04367.x
Subject(s) - flavin mononucleotide , chemistry , singlet oxygen , flavin group , photochemistry , nicotinamide mononucleotide , spinach , oxygen , enzyme , biochemistry , nicotinamide adenine dinucleotide , nad+ kinase , organic chemistry
All the activities of the nitrate reductase complex from spinach are irreversibly inactivated by irradiation of the enzyme with blue light in the presence of flavin mononucleotide. The photoinactivation requires oxygen and is prevented by ethylenediaminetetraacetic acid and by reduced nicotinamide adenine dinucleotide, but not by superoxide dismutase plus catalase. On the other hand, the inactivation is markedly enhanced in 77% deuterated water and it is suppressed by the singlet oxygen quenchers azide, histidine and tryptophan. All these results suggest that singlet oxygen generated by light absorption by flavin mononucleotide, rather than excited flavin mononucleotide or other oxygen species, is the primary agent involved in the photooxidative inactivation of the enzyme.