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PHOTOREDUCTION OF CYTOCHROME b551 OF PARTIALLY PURIFIED NEUROSPORA NITRATE REDUCTASE VIA ITS INTERNAL FLAVIN
Author(s) -
Ninnemann Helga
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.tb02579.x
Subject(s) - neurospora crassa , flavin group , cytochrome , nitrate reductase , neurospora , chemistry , absorbance , biochemistry , nitrate , reductase , photochemistry , enzyme , mutant , chromatography , organic chemistry , gene
— Nitrate reductases (NR) from NR‐normal Neurospora crassa mutant albino band and from NR‐defective mutantsnit–1 andnit–3 were isolated and partially purified in order to test the photo‐reducibility of their cytochrome b 557 via the NR‐internal FAD. Photoreducibility with blue light of the isolated enzyme was observed as absorbance increase at 423, 524 and553–557 nm. It was independent of NADPH‐nitrate reductase activity and could be induced if the dissociable FAD was not lost in the isolation procedure. The photoreduction of cytochrome b 557 was readily reversible due the high autoxi‐dation rate of this cytochrome. Therefore, anaerobic conditions are required for photoreduction with low light intensities. If aerobic conditions are applied, high intensities become necessary to overcome the simultaneous cytochrome h 557 oxidation.