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PHOTOCHEMICAL and ENZYMATIC REDOX TRANSFORMATIONS OF REDUCED FORMS OF COENZYME NADP+
Author(s) -
Czochralska B.,
Bojarska E.,
Pawlicki K.,
Shugar D.
Publication year - 1990
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.1751-1097.1990.tb01731.x
Subject(s) - dimer , chemistry , photochemistry , cofactor , redox , oxygen , peroxidase , anaerobic exercise , enzyme , irradiation , inorganic chemistry , biochemistry , organic chemistry , biology , physiology , physics , nuclear physics
— The two reduced forms of NADP+, NADPH and its dimer (NADP), on irradiation in aqueous medium at 365 nm, are converted to enzymatically active NADP+, with accompanying formation of H 2 O 2 . The rate of photooxidation of NADPH is strongly dependent on the presence of oxygen, but that of (NADP) 2 is similar under aerobic and anaerobic conditions. In the presence of oxygen, but not in its absence, O 2 is an intermediate in the reaction. Generation of H 2 O 2 under anaerobic conditions, confirmed by the fact that presence of peroxidase in irradiated solutions of (NADP) 2 enhances photooxidation of the latter, is ascribed to attack on water of the excited dimer. Under anaerobic conditions at pH 9.5, Fe(EDTA) 2 + and Fe(CN) 4 increase the rate of photooxidation of NADP dimer two‐fold. γ ‐Irradiation of (NADP) 2 at pH 9.5 in the presence of N 2 O results in 80% conversion to enzymatically active NADP + . A mechanism for photooxidation of (NADP) 2 under anaerobic conditions is suggested, and some relevant biological implications are presented.