Multiple Forms and Intracellular Localization of Uridine Diphosphate Glucose Pyrophosphorylase in Avena sativa

Uridine diphosphate glucose pyrophosphorylase was isolated separately from Avena sativa leaves, roots, and etiolated coleoptiles and purified by ammonium sulfate fractionation, DEAE-Sephadex chromatography and polyacrylamide gel electrophoresis. There was no difference in the enzyme from the different tissue types with respect to properties exhibited during the purification procedure. A small portion of the enzyme from all three sources was found to be particulate when homogenized in aqueous sucrose media. Characterization of the particulate form by discontinuous sucrose density gradient showed the enzyme to be located at two different densities, one of which corresponded to chloroplasts in the leaves and plastids in the coleoptiles and roots. Homogenization and fractionation of the oat leaves using the nonaqueous media, hexane, and carbon tetrachloride, resulted in 50 to 60% of the enzyme being associated with chloroplasts and the remainder being associated with other membranous material. These data indicate that the enzyme from oat leaves, roots, and etiolated coleoptiles has multiple intracellular locations, and it is suggested that compartmentation of this enzyme may be a mechanism for regulation of uridine diphosphate glucose metabolism in oats.