title: Enzymic capacities of amyloplasts from wheat (Triticum aestivum) endosperm.
abstract: Lysates of protoplasts from the endosperm of developing grains of wheat (Triticum aestivum) were fractionated on density gradients of Nycodenz to give amyloplasts. Enzyme distribution on the gradients suggested that: (i) starch synthase and ADP-glucose pyrophosphorylase are confined to the amyloplasts; (ii) pyrophosphate: fructose-6-phosphate 1-phosphotransferase and UDP-glucose pyrophosphorylase are confined to the cytosol; (iii) a significant proportion (23-45%) of each glycolytic enzyme, from phosphoglucomutase to pyruvate kinase inclusive, is in the amyloplast. Starch synthase, ADP-glucose pyrophosphorylase and each of the glycolytic enzymes showed appreciable latency when assayed in unfractionated lysates of protoplasts. No activity of fructose-1,6-bisphosphatase was found in amyloplasts or in homogenates of endosperm. Antibody to plastidic fructose-1,6-bisphosphatase did not react positively, in an immunoblot analysis, with any protein in extracts of wheat endosperm. It is argued that wheat endosperm lacks significant plastidic fructose-1,6-bisphosphatase and that carbon for starch synthesis does not enter the amyloplast as a C-3 compound but probably as hexose phosphate.
authors.affiliation: Botany School, University of Cambridge, U.K.
authors.forename: G
authors.initials: G
authors.lastname: Entwistle
authors.forename: T A
authors.initials: TA
authors.lastname: Rees
mesh_terms: D000906:Antibodies; D050260:Carbohydrate Metabolism; D003594:Cytoplasmic Granules / Q000201:enzymology*; D006597:Fructose-Bisphosphatase / Q000378:metabolism; D005635:Fructosediphosphates / Q000378:metabolism; D005636:Fructosephosphates / Q000378:metabolism; D015151:Immunoblotting; D010770:Phosphotransferases / Q000276:immunology; D011523:Protoplasts / Q000378:metabolism; D014908:Triticum / Q000201:enzymology*
chemical_list: D000906:Antibodies; D005635:Fructosediphosphates; D005636:Fructosephosphates; C027618:fructose-6-phosphate; D010770:Phosphotransferases; C022502:pyrophosphate-fructose 6-phosphate 1-phosphotransferase; D006597:Fructose-Bisphosphatase; C029063:fructose-1,6-diphosphate