Starch Biosynthesis. II. The Statistical Model for Amylopectin and Its Precursor Plant Glycogen

Autor: Stig R. Erlander
Rok vydání: 1998
Předmět:
Zdroj: Starch - Stärke. 50:275-285
ISSN: 1521-379X
0038-9056
Popis: A modified Meyer model as well as a model containing all possible randomly branched structures (a statistical model) were used for both a precursor glycogen and its amylopectin and were modified by placing short A-chains into the interior part of the structure and thus eliminating some of the longer chains. Debranching of the exterior A-chains of the glycogen model produced amylopectin plus 25% amylose with the assumption that only those A-chains removed from the glycogen were converted into amylose. A comparison of the debranched amylopectin model with debranched wheat and barley amylopectins showed the polymodal behavior of debranched amylopectins can be duplicated with a model system that has inner A-chains and a Poisson size distribution. Branching of external chains of glycogen without chain extension after synthesis has stopped plus inner A-chains can explain the increase (from glycogen to amylopectin) in the A/B chain ratio, the existance of cluster structures. and the observed decrease in branching (8% to 4%) in going from dent, waxy and sweet corn glycogens to their respective amylopectins (or 6.3% to 2.0% for glycogen to amylopectin in ae corn). Disperseable (as in waxy) or indispersable high molecular weight aggregates may be due to different amylopectin-protein complexes.
Databáze: OpenAIRE
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