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FLAVIN‐MEDIATED PHOTOREACTIONS IN ARTIFICIAL SYSTEMS: A POSSIBLE MODEL FOR THE BLUE‐LIGHT PHOTORECEPTOR PIGMENT IN LIVING SYSTEMS *
Author(s) -
Schmidt W.,
Butler W. L.
Publication year - 1976
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.1751-1097.1976.tb06799.x
Subject(s) - flavin group , photochemistry , chemistry , cytochrome , superoxide , oxygen , hydrogen peroxide , cytochrome c , azide , hemeprotein , photostimulation , heme , biochemistry , organic chemistry , enzyme , mitochondrion
— The photoreduction of cytochrome c and the photostimulation of oxygen uptake were studied in solutions of flavin and cytochrome as a possible model system for similar photoreactions which have been observed in vivo. Light causes the photoreduction of the flavin. Under aerobic conditions the photoreduced flavin reacts with oxygen to form the superoxide anion which in turn can reduce cytochrome c. Dismutation of the superoxide anions forms hydrogen peroxide which mediates the dark oxidation of the photoreduced cytochrome. Superoxide formation and dismutation also account for the light‐induced oxygen uptake. Action spectra confirm the role of flavin in the photoreduction of cytochrome c and the photostimulation of oxygen uptake. Under anaerobic conditions the photoreduced flavin reduces cytochrome c directly. In the presence of an electron donor only catalytic amounts of flavin are required. In the absence of an added electron donor flavin itself can act as the electron donor if substrate amounts are present. Azide inhibits all of these flavin‐mediated photoresponses. Azide also inhibits the photoreduction of cytochrome b which occurs in the mycelium of Newospora.