Premium
PHOTOREACTIVATION BY TRIPLET FLAVIN and PHOTOINACTIVATION BY SINGLET OXYGEN OF Neurospora crassa NITRATE REDUCTASE *
Author(s) -
Fritz Bernhard J.,
Ninnemann Helga
Publication year - 1985
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.1751-1097.1985.tb03445.x
Subject(s) - flavin group , photolyase , photochemistry , chemistry , neurospora crassa , singlet oxygen , riboflavin , nitrate reductase , neurospora , oxygen , triplet state , reductase , nitrate , enzyme , biochemistry , organic chemistry , molecule , mutant , dna repair , gene
— In the present paper the mechanism of photoreactivation and photodestruction of partially purified nitrate reductase from Neurospora crassa was investigated. For both photoreactions exogenous flavin was needed; the rates of the photoreactions depended on the concentration of free flavin in the irradiated sample. Their efficiency as photoreceptors increased in the sequence FAD–FMN–riboflavin. No effect of enzyme‐bound flavin as photoreceptor was found in these photoreactions. Photoreactivation of nitrate reductase inactivated by reduction in the presence of KCN is due to its reaction with flavins in their triplet state. Photodestruction is due to singlet oxygen generated from triplet flavin in the presence of oxygen. Rate constants are estimated to be k = 1–5 × 10 ‐1 M ‐1 s ‐1 for the reaction of nitrate reductase with the flavin triplet (photoreactivation) and k = 5 × 10 ‐1 M ‐1 s ‐1 for the reaction with singlet oxygen (photodestruction).