Skip to main content
U.S. Department of Energy
Office of Scientific and Technical Information

Influence of pH upon the Warburg effect in isolated intact spinach chloroplasts. I. Carbon dioxide photoassimilation and glycolate synthesis

Journal Article · · Plant Physiol.; (United States)
DOI:https://doi.org/10.1104/pp.59.4.530· OSTI ID:7212927
The influence of pH upon the O/sub 2/ inhibition of /sup 14/CO/sub 2/ photoassimilation (Warburg effect) was examined in intact spinach (Spinacia oleracea) chloroplasts. With conditions which favored the Warburg effect, i.e. rate-limiting CO/sub 2/ and 100 percent O/sub 2/, O/sub 2/ inhibition was greater at pH 8.4 to 8.5 than at pH 7.5 to 7.8. At pH 8.5, as compared with 7.8, there was an enhanced /sup 14/C-labeling of glycolate, and a decrease of isotope in some phosphorylated Calvin cycle intermediates, particularly triose-phosphate. The /sup 14/C-labeling of starch was also more inhibited by O/sub 2/ at higher pH. The enhanced synthesis of glycolate during /sup 14/CO/sub 2/ assimilation at higher pH resulted in a diminution in the level of phosphorylated intermediates of the Calvin cycle, and this was apparently a causal factor of the increased severity of the Warburg effect. The /sup 14/C-labeling profiles have been interpreted in terms of a ''CO/sub 2/''-sensitive as well as a ''CO/sub 2/''-insensitive mechanism for glycolate synthesis. Both mechanisms functioned optimally at the higher pH and both responded to O/sub 2/.
Research Organization:
Brandeis Univ., Waltham, MA
OSTI ID:
7212927
Journal Information:
Plant Physiol.; (United States), Journal Name: Plant Physiol.; (United States) Vol. 59:4; ISSN PLPHA
Country of Publication:
United States
Language:
English