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The control of amylose synthesis

Amylose - Wikipedia

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Waxy Maize Starch Versus Dextrose/Maltodextrin

Although it is well known that elongation of amylose chains is predominantly by GBSSI and that amylose branches are formed by starch branching enzymes (SBEs) (Denyer et al. ; Ball et al. ), little is known about the details of how the individual isoforms of SBE and starch synthase (SS) contribute to the amylose chain-length distribution (CLD). The lengths, and the relatively few but significant numbers, of these chains influence functional properties such as digestion rate and location, and mouth-feel (Syahariza et al. ). Previous studies have shown that debranched amylose distributions have at least two distinct groups (Ward et al. ; Syahariza et al. ; Li et al. ; Witt et al. ), which are here referred to as the short and long amylose features. Their synthesis may be controlled by different enzyme combinations.

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The shapes of the amylose CLDs, ratios of AM1 AUP and of AM2 AUP and the XAM2 value of Daohuaxiang rice show clear differences from those of Koshihikari (Fig. and Table ). Both wild type WXJ and Koshihikari have higher β(iv) (Table ) and larger AUP of AM1 than the other two samples. This could indicate that besides GBSSI, enzymes responsible for synthesis of long amylopectin chains (such as the fourth enzyme set) might also play an important role in amylose synthesis. The samples with lower h(v/i) value (wild-type WXJ and Koshihikari) have larger ratios of AM1 AUP, which also might indicate that the amount of long amylopectin and short amylose chains are negatively correlated. BEI is one of the enzymes that can affect synthesis of short amylose chains, as discussed above. The effect of SS is not analyzed in this study; however, SS involving long amylopectin chain synthesis might be able to affect short amylose chain synthesis. SSIII, which mainly contributes to the elongation of long inner amylopectin (B2, B3) chains (Edwards et al. ; Lloyd et al. ), could be another enzyme involved in synthesis of short amylose chains.

Modifying the Surface Properties of Superparamagnetic …

the amylopectin-synthesising isoforms of starch synthase are important to the understanding of the control of amylose synthesis.

The results suggest that while GBSSI is the predominant enzyme controlling the synthesis of longer amylose chains, some branching enzymes (such as BEI and BEIIb) also play important roles in the synthesis of shorter amylose chains.

1 Starch is synthesized and stored in plastids; chloroplasts in leaves andspecialized organelles in storage tissues termed amyloplasts. The starch is densly packed in structures known as starch granules,often as starch crystals. Starch granules, which contain 0.1-1%lipid and 0.05-0.5% protein, vary in size from 100µm. Starch granule structure and synthesis is shown in Fig.

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We achieved to synthesize a novel inclusion supramolecular polymer composed of continuum of amylose-poly(tetrahydrofuran) (PTHF) inclusion complexes by phosphorylase-catalyzed enzymatic polymerization using a maltoheptaose-PTHF conjugate according vine-twining polymerization manner. The 1H NMR and X-ray diffraction measurements indicated the presence of the inclusion complex structure in the product. The GPC peak of the amylose segment, which was dissociated by heating the vine-twining polymerization product, shifted to the lower molecular weight region, compared with that of the product, supporting the structure of the inclusion supramolecular polymer. The product by the G-1-P/G7-PTHF feed ratio = 100 was the supramolecular polymer composed of continuum of the amylose-PTHF inclusion complexes, whereas both inclusion complexes and amylose double helixes were present in the product by the G-1-P/G7-PTHF feed ratio over 200.

Amylose chains in the wild-type and mutant rice samples examined here can be divided into two different groups, long and short, with different ranges of degrees of polymerization showing distinct features in the chain-length distribution. The present results show that these two amylose groups have different dominant biosynthesis enzymes. As is well known, long amylose chains are mainly synthesized by GBSSI. The synthesis of short amylose chains is found here to be controlled not only by GBSSI but also starch branching enzymes, which are also involved in long amylopectin chain synthesis. Because these smaller amylose chains have significant effects on functional properties such as mouth-feel and digestibility (Syahariza et al. ; Syahariza et al. ), this finding has potential application in the development of improved crop varieties.

18/05/2005 · Enzymatic synthesis of amylose ..
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(2011) Exploiting leaf starch synthesis as a transient ..

We recently achieved to synthesize a novel supramolecular polymer, which was composed of continuum of the amylose-poly(L-lactide) (PLLA) inclusion complexes, was produced when a G7-functionalyzed PLLA was used as a primer-guest conjugate substrate in the vine-twining polymerization. In this approach, a propagating amylose chain started from G7 moiety in the primer-guest conjugate by the phosphorylase catalysis includes a polyester, PLLA, segment in the other substrate. Such special type of the vine-twining polymerization among the substrates successively takes place, giving rise to the novel inclusion supramolecular polymer composed of amylose and PLLA. This vine-twining polymerization approach for the supramolecular polymer has inspired us to be applicable to other hydrophobic polymers. Because it was found to form the inclusion complex with amylose, in this paper, we employed a polyether, poly(tetrahydrofuran) (PTHF), and demonstrated the synthesis of inclusion supramolecular polymer composed of amylose and PTHF (amylose-PTHF) by means of the vine-twining polymerization using G7-functionalized PTHF (G7-PTHF) as a primer-guest conjugate.

Improved understanding of rice amylose biosynthesis …

Starch granules are composed of two types of glucose polymer, amylose and amylopectin, that differ in size and structure. One of the most intriguing challenges in understanding starch synthesis is to explain the apparently simultaneous synthesis of two such different polymers. One isoform of starch synthase, GBSSI, is responsible for amylose synthesis but can also contribute to amylopectin syn-thesis. The factors which determine the partitioning of GBSSI activity between these two processes are largely unknown. Understanding the properties of GBSSI and how these differ from the proper-ties of the amylopectin-synthesising isoforms of starch synthase are important to the understanding of the control of amylose synthesis. In this review, we will describe how the synthesis of amylose and amylopectin are integrated and what factors may determine the relative amounts of these two poly-mers. Key words: starch – amylose – amylopectin – starch synthase – GBSSI – malto-oligosaccharide Abbreviations: GBSSI granule-bound starch synthase I. – SS starch synthase. – ADPG adenosine 5′-diphospho-glucose. – MOS malto-oligosaccharide. – dp degree of polymerization

Amylose synthesis was obtained in vitro from purified ..

In conclusion, we achieved to synthesize the novel inclusion supramolecular polymer composed of amylose and PTHF by vine-twining polymerization using a primer-guest polymer conjugate, G7-PTHF. The supramolecular polymer, amylose-PTHF, was composed a polymeric continuum of some amylose moieties included PTHF moieties. The product by the G-1-P/G7-PTHF feed ratio = 100 was the supramolecular polymer composed of continuum of the amylose-PTHF inclusion complexes, whereas both inclusion complexes and amylose double helixes were present in the product by the G-1-P/G7-PTHF feed ratio = 200 and 300. Because this supramolecular polymer, which is composed of bio-related component, amylose, is novel and has a possibility of new biobased hybrid material, it has potential for practical applications as a new type of amylose-based material in the future.

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