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PHOTOREGULATION OF NITRATE UTILIZATION IN GREEN ALGAE AND HIGHER PLANTS *
Author(s) -
APARICIOH Pedro J.,
Balandin Teresa,
Maurino Sofía G.,
Maldonado José M.
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.tb01645.x
Subject(s) - nitrate reductase , methylene blue , chemistry , spinach , hydroxylamine , nitrate , incubation , flavin group , reductase , singlet oxygen , photochemistry , biochemistry , enzyme , photocatalysis , organic chemistry , oxygen , catalysis
— Nitrate reductase from eukaryotes can be reversibly inactivated, blue light being an effective activating agent both in vitro and in vivo. Hydroxylamine proved to be a powerful inactivating agent of Ankistrodesmus braunii nitrate reductase. Irradiation with blue light of NH 2 OH‐inactivated nitrate reductase, specially in the presence of μM amounts of FAD, promoted the recovery of the enzyme activity. Similarly, photoexcited methylene blue reactivated spinach nitrate reductase. On the other hand, in vitro nitrate reductase is highly susceptible to photodynamic inactivation caused by singlet O 2 . Aerobic incubation of the active spinach enzyme with either FMN or methylene blue under either blue or red light respectively led to its irreversible inactivation. Irradiation of frozen and thawed spinach leaf discs also promoted, in situ , an irreversible inactivation of nitrate reductase, provided that 6 2 was present in the incubation mixture. Thus, either in vitro or in situ , light can cause two quite different responses of nitrate reductase, its blue light‐dependent photoactivation in a flavin sensitized reaction and its photodynamic inactivation in a singlet O 2 ‐dependent process.