Biosynthesis of starch in chloroplasts.
The enzymic synthesis of ADP-glucose and UDP-glucose by chloroplastic pyrophosphorylase of bean and rice leaves has been demonstrated by paper chromatographic techniques. In both tissues, the activity of UDP-glucose-pyrophosphorylase was much higher than ADP-glucose-pyrophosphorylase. Glycerate-3-phosphate, phosphoenolpyruvate and fructose-1,6-diphosphate did not stimulate ADP-glucose formation by a pyrophosphorylation reaction. The major metabolic pathway for UDP-glucose utilization appears to be the synthesis of either sucrose or sucrose-P. On the other hand, a specific precursor role of ADP-glucose for synthesizing chloroplast starch by the ADP-glucose-starch transglucosylase reaction is supported by the coupled enzyme system of ADP-glucose-pyrophosphorylase and transglucosylase, isolated from chloroplasts. None of the glycolytic intermediates stimulated the glucose transfer in the enzyme sequence of reaction system employed.
D002736:Chloroplasts / Q000201:enzymology*; D002852:Chromatography, Ion Exchange; D012275:Oryza; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D010945:Plants, Edible; D013213:Starch / Q000096:biosynthesis*
D013213:Starch; D010744:Phosphoric Monoester Hydrolases