Abstract
THE relation between bicarbonate concentration and rate of photosynthesis in isolated spinach chloroplasts at pH 7.6 is initially linear, though it becomes asymptotic at 1.0–1.2 mM, with the half-maximal rate (apparent Km) at 0.6 mM bicarbonate1. This figure must be reconciled with the apparent Km (bicarbonate) of ribulose diphosphate carboxylase, which is 5–20 mM depending on the cofactor supplement2,3. Accordingly, suggestions have been made that chloroplasts may concentrate CO2 (ref. 4) or that the carboxylation of ribulose diphosphate may undergo activation in vivo5.
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References
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EVERSON, R. Bicarbonate Equilibria and the Apparent Km (HCO3−) of Isolated Chloroplasts. Nature 222, 876 (1969). https://doi.org/10.1038/222876a0
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DOI: https://doi.org/10.1038/222876a0
