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MAGNESIUM ACTIVATION OF PHOTOSYNTHETIC CO 2 ‐FIXATION IN A RECONSTITUTED CHLOROPLAST SYSTEM
Author(s) -
LILLEY R. McC.,
HOLBOROW K.,
WALKER D. A.
Publication year - 1974
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1974.tb01292.x
Subject(s) - carboxylation , photosynthesis , bicarbonate , oxygen evolution , carbon fixation , kinetics , chloroplast , ribulose , chemistry , rubisco , magnesium , biophysics , botany , biochemistry , biology , electrochemistry , catalysis , physics , gene , organic chemistry , electrode , quantum mechanics
S ummary Measurements of O 2 ‐evolution by a reconstituted chloroplast system showed that photosynthetic electron transport and 3‐phosphoglycerate reduction proceed at rapid rates in the presence of 0.5‐1 ran MgCl 2 . However, to obtain maximal rates of CO 2 ‐dependent O 2 ‐evolution under these conditions, it was necessary to increase the Mg concentration to 5 mM (70‐90% of the maximum rate was observed at 2.5 mM Mg). Rapid rates of CO 2 ‐dependent O 2 evolution were also recorded at 1 mM Mg when the bicarbonate concentration was increased from 1 to 40 mM. Simultaneous measurements of 14 CO 2 fixation and O 2 evolution in the presence of ribulose‐1, 5‐diphosphate confirmed that the additional Mg was required for the carboxylation step and showed that the Mg activation was a more rapid process than the kinetics of CO 2 ‐dependent O 2 evolution might suggest.