Phosphorylated alpha(1 leads to 4) glucans as substrate for potato starch-branching enzyme I

The possible involvement of potato (Solanum tuberosum L.) starch-branching enzyme I (PSBE-I) in the in vivo synthesis of phosphorylated amylopectin was investigated in in vitro experiments with isolated PSBE-I using 33P-labeled phosphorylated and 3H end-labeled nonphosphorylated alpha(1 leads to 4)...

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Bibliographic Details
Published in:Plant physiology (Bethesda) 1998-07, Vol.117 (3), p.869-875
Main Authors: Vikso-Nielsen, A. (Royal Veterinary and Agricultural University, Copenhagen, Denmark.), Blennow, A, Nielsen, T.H, Moller, B.L
Format: Article
Language:English
Subjects:
ACTIVIDAD ENZIMATICA
ACTIVITE ENZYMATIQUE
Agronomy. Soil science and plant productions
ALMIDON
AMIDON
Biochemistry and Enzymology
Biological and medical sciences
BIOSINTESIS
BIOSYNTHESE
BIOSYNTHESIS
CHEMICAL COMPOSITION
Chromatography
COMPOSICION QUIMICA
COMPOSITION CHIMIQUE
Economic plant physiology
Elution
ENZIMAS
ENZYME
ENZYMES
ENZYMIC ACTIVITY
FOSFORILACION
Fundamental and applied biological sciences. Psychology
Glucans
Industrial plants
ISOTOPE RADIOACTIF
Metabolism
METABOLITE
METABOLITES
METABOLITOS
Net assimilation, photosynthesis, carbon metabolism. Photorespiration, respiration, fermentation (anoxia, hypoxia)
Nutrition. Photosynthesis. Respiration. Metabolism
PECTINAS
PECTINE
PECTINS
Phosphates
PHOSPHORYLATION
Photosynthesis, respiration. Anabolism, catabolism
Plant physiology and development
PROTEINAS
PROTEINE
PROTEINS
Radioactive decay
RADIOACTIVE TRACERS
RADIOISOTOPES
RADIOISOTOPOS
SOLANUM TUBEROSUM
STARCH
Starches
TUBERCULE
TUBERCULO
TUBERS
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Summary:The possible involvement of potato (Solanum tuberosum L.) starch-branching enzyme I (PSBE-I) in the in vivo synthesis of phosphorylated amylopectin was investigated in in vitro experiments with isolated PSBE-I using 33P-labeled phosphorylated and 3H end-labeled nonphosphorylated alpha(1 leads to 4) glucans as the substrates. From these radiolabeled substrates PSBE-I was shown to catalyze the formation of dual-labeled (3H/33P) phosphorylated branched polysaccharides with an average degree of polymerization of 80 to 85. The relatively high molecular mass indicated that the product was the result of multiple chain-transfer reactions. The presence of alpha(1 leads to 6) branch points was documented by isoamylase treatment and anion-exchange chromatography. Although the initial steps of the in vivo mechanism responsible for phosphorylation of potato starch remains elusive, the present study demonstrates that the enzyme machinery available in potato has the ability to incorporate phosphorylated alpha(1 leads to 4) glucans into neutral polysaccharides in an interchain catalytic reaction. Potato mini tubers synthesized phosphorylated starch from exogenously supplied 33PO4(3-) and [U-14C]Glc at rates 4 times higher than those previously obtained using tubers from fully grown potato plants. This system was more reproducible compared with soil-grown tubers and was therefore used for preparation of 33P-labeled phosphorylated alpha(1 leads to 4) glucan chains
ISSN:0032-0889
1532-2548
DOI:10.1104/pp.117.3.869