Photosynthetic Intermediates, The Warburg Effect, and Glycolate Synthesis in Isolated Spinach Chloroplasts ¹

Abstract

Increasing levels of CO₂ have been shown to stimulate the rate of photosynthesis, eliminate the oxygen inhibition of photosynthesis (Warburg effect), and decrease glycolate formation in isolated spinach chloroplasts. Ribose 5-phosphate and fructose 1,6-diphosphate at concentrations of 5 to 10 μm also stimulate the rate of plastid photosynthesis and eliminate the Warburg effect. In contrast to the effect of high CO₂ levels, these sugar phosphates have little effect on glycolate formation. Evidence is presented to show that the level of intermediates of the photosynthetic carbon reduction cycle may influence the Warburg effect in vivo. It is postulated that the formation of glycolate is not the causal factor of the Warburg effect.

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This research was generously supported by the National Science Foundation Grant GB 29126 X and by a training grant of the National Institute of Health, Grant GM 1586.