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

Abstract

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.

Starch Biosynthesis. I. The Size Distributions of Amylose and Amylopectin and Their Relationships to the Biosynthesis of Starch

“…The results presented here thus support the proposal that starch is made by the precursor glycogen mechanism postulated in 1958 [1] and extended elsewhere [10,23] and that amylose can not be a precursor to amylopectin because of the difference in the size distribution of the linear chains of the two polymers. Furthermore, it is concluded that steric hindrance forces the production of "hidden" A-chains (those A-chains not removed in the conversion of plant glycogen into amylopectin and amylose).…”

“…It is evident that the sharp Poisson size distribution can not explain the results. The A-B condensation polymer, although a much broader curve, is still shy of the experimental results and thus this plus the results of Griffin et al [31], as well as the results given below and elsewhere [23], indicate that a part of the branched amylose may be non-statistically formed, whereas another part of the branched amylose appears to consist of randomly (statistically formed) A-R-B 2 type branched amylose molecules, particularly with the observed wide variations in branch lengths [13,32], as well as the broader A-B type size distribution of the linear amylose chains.…”

“…These hidden A-chains in, for example, the third tier from the exterior of the molecule, may have a different degree of polymerization than those in the fifth tier. And 2) a remnant of the polymer produced in the exterior tier of the amylopectin when branching of the exterior chains of the precursor glycogen has occurred without chain extension (see [10,23]). …”

Changes of Thermodynamic and Structural Properties of Potato Starches (Udacha andAcrosil Varieties) during Biosynthesis

“…According to [4], an increase in amylose content in potato starches leads to an increase in granular sizes and molecular weights of amylose and amylopectin. Recently, some concepts concerning mechanisms of amylose and amylopectin biosynthesis were considered by Erlander [7,8] and Ball et al [9]. However, formation processes of different supramolecular polymorphous structures in starch granules remain incompletely understood.…”