Starch biosynthesis: sucrose as a substrate for the synthesis of a highly branched component found in 12 varieties of starches.
D-[14C]glucose was incorporated into starch when 12 varieties of starch granules were incubated with [14C]sucrose. Digestion of the 14C-labeled starches with porcine pancreatic alpha amylase showed that a high percentage (16.1-84.1%) of the synthesized starch gave a relatively high molecular weight alpha-limit dextrin. Hydrolysis of the 12 varieties of starch granules by alpha amylase, without sucrose treatment, also gave an alpha-limit dextrin, ranging in amounts from 0.51% (w/w) for amylomaize-7 starch to 8.47% (w/w) for rice starch. These alpha-limit dextrins had relatively high molecular weights, 2.47 kDa for amylomaize-7 starch to 5.75 kDa for waxy maize starch, and a high degree of alpha-(1-->6) branching, ranging from 15.6% for rice starch to 41.1% for shoti starch. ADPGlc and UDPGlc did not synthesize a significant amount (1-2%) of the branched component, suggesting that sucrose is the probable substrate for the in vivo synthesis of the component and that sucrose is not first converted into a nucleotide-glucose diphosphate intermediate.
Mukerjea
Rupendra
R
Department of Biochemistry, Laboratory of Carbohydrate Chemistry and Enzymology, Iowa State University, 4252 Molecular Biology Bldg, Ames, IA 50011, USA.
Robyt
John F
JF
D000245:Adenosine Diphosphate Glucose / Q000378:metabolism; D000818:Animals; D002854:Chromatography, Paper; D002855:Chromatography, Thin Layer; D003912:Dextrins / Q000032:analysis / Q000737:chemistry; D019075:Electrophoresis, Capillary; D005947:Glucose / Q000032:analysis / Q000378:metabolism; D006868:Hydrolysis; D007517:Isoamylase / Q000378:metabolism; D008320:Maltose / Q000031:analogs & derivatives / Q000032:analysis; D008970:Molecular Weight; D009844:Oligosaccharides / Q000032:analysis; D025942:Oligosaccharides, Branched-Chain / Q000096:biosynthesis* / Q000737:chemistry; D010944:Plants / Q000737:chemistry / Q000378:metabolism*; D011134:Polysaccharides / Q000032:analysis / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D013213:Starch / Q000096:biosynthesis* / Q000737:chemistry; D013214:Starch Synthase / Q000378:metabolism*; D013379:Substrate Specificity; D013395:Sucrose / Q000378:metabolism*; D013552:Swine; D014312:Trisaccharides / Q000032:analysis; D014532:Uridine Diphosphate Glucose / Q000378:metabolism; D000516:alpha-Amylases / Q000378:metabolism
D003912:Dextrins; D009844:Oligosaccharides; D025942:Oligosaccharides, Branched-Chain; D011134:Polysaccharides; D014312:Trisaccharides; D000245:Adenosine Diphosphate Glucose; D013395:Sucrose; C008317:maltotriose; D008320:Maltose; C008315:maltodextrin; D013213:Starch; C009819:maltotetraose; D013214:Starch Synthase; D000516:alpha-Amylases; D007517:Isoamylase; D005947:Glucose; D014532:Uridine Diphosphate Glucose