Regulation of Carbohydrate Breakdown of Chlorella Mutant No. 20, Studied by ^<31>P NMR Spectroscopy and Enzymatic Analysis : 1. Regulation under Blue Light Conditions

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The regulation of carbohydrate degradation, especially of its glycolytic part, is studied in darkness and under blue light conditions in the chlorophyll-free Chlorella mutant no. 20. The mass action ratios of glycolytic reactions are calculated from the concentrations of the respective intermediates, measured via enzymatic analysis and ^<31>P NMR spectroscopy. Comparison with the equilibrium constants indicates that the reactions catalyzed by hexokinase, phosphofructokinase, and pyruvate kinase are able to control the glycolytic pathway. Blue light illumination leads to rapid changes in the level of various metabolites. The decrease in PEP proves the regulatory role of pyruvate kinase in vivo, a finding supported by the crossover plot as well as by the move of the mass action ratio towards equilibrium. Also, the starch degrading enzymes phosphorylase and possibly amylase, but not phosphofructokinase, seem to be involved in the regulation of carbohydrate breakdown in blue light. The kinetics of the different blue light responses clearly indicate that not the increase in respiratory O_2 uptake, but an appropriate change in the concentration of effectors of the regulatory enzymes pyruvate kinase, phosphorylase, and maybe amylase is a primary blue light effect in the Chlorella mutant. The involvement of a proton pump seems to be ruled out by the constant intracellular pH measured by in vivo ^<31>P NMR spectroscopy.
日本植物生理学会の論文