Premium
KINETICS OF CHLOROPLAST‐MEDIATED PHOTOXIDATION OF DIKETOGULONATE *
Author(s) -
HABERMANN HELEN M.,
HANDEL MARY ANN,
McKELLAR PENELOPE
Publication year - 1968
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.1751-1097.1968.tb08007.x
Subject(s) - dcmu , ferricyanide , photochemistry , oxygen evolution , photosystem ii , chloroplast , chemistry , photosystem i , flavin group , electron transport chain , hill reaction , tricine , quantum yield , oxygen , photosynthesis , inorganic chemistry , electrochemistry , biochemistry , organic chemistry , fluorescence , physics , electrode , enzyme , quantum mechanics , gene
— Illuminated chloroplasts can mediate a photoxidation of diketogulonic acid (DKGA) with rates of oxygen uptake equivalent to rates of Hill reactions with ferricyanide or quinone. The photoxidation of DKGA is sensitive to dichlorophenyl dimethylurea (DCMU) and exhibits the drop in quantum yield at long wavelengths characteristic of photosystem II. Still, the reaction is only partially inactivated by heating chloroplasts at 50° for 10 min (which destroys oxygen evolution). The photoxidation is inhibited by copper and detergents; and is stimulated by added flavin (or methyl viologen) and manganous ions. A model system containing Mn 3+ (as manganipyrophosphate) and DKGA, mimics the chloroplast system. Pre‐illuminated chloroplast suspensions can be substituted for Mn 3+ in the model dark reaction. It seems that a light‐dependent oxidation of Mn 2+ to Mn 3+ by photosystem II is the essential contribution of the chloroplasts. Electrons from Mn 2+ move through the electron transport system to ferricyanide or to photosystem I where, via flavin (or methyl viologen), oxygen is reduced to H 2 O 2 .