Influence of pH upon the Warburg Effect in Isolated Intact Spinach Chloroplasts

Abstract

The light-dependent synthesis of glycolate derived from fructose 1,6-diphosphate, ribose 5-phosphate, or glycerate 3-phosphate was studied in the intact spinach (Spinacia oleracea) chloroplasts in the absence of CO₂. Glycolate yield increased with an elevation of O₂, pH, and the concentration of the phosphorylated compound supplied. No pH optimum was observed as the pH was increased from 7.4 to 8.5. The average maximal rate of glycolate synthesis was 50 μmoles per milligram chlorophyll per hour while the highest rate observed was 92 with 2.5 mm fructose 1,6-diphosphate in 100% O₂. The highest yields of glycolate synthesized from fructose 1,6-diphosphate, ribose 5-phosphate, or glycerate 3-phosphate were 0.14, 0.24, and 0.30, respectively, on a molar basis.