scholarly journals Biosynthesis of waxy starch – a review

2017 ◽  
Vol 63 (No. 8) ◽  
pp. 335-341 ◽  
Author(s):  
Šárka Evžen ◽  
Dvořáček Václav
Keyword(s):  
Plant Breeding ◽  
Metabolic Pathways ◽  
Special Form ◽  
Starch Biosynthesis ◽  
Starch Synthase ◽  
Conversion Process ◽  
Starch Synthases ◽  
Competent Cells ◽  
Waxy Starch ◽  
Starch Conversion

Starch comprises nearly linear amylose and branched amylopectin, whilst waxy starches are a special form, containing almost exclusively amylopectin. Modern techniques in plant breeding together with new data from starch biosynthesis research have enabled new food and non-food uses of waxy starches. This paper describes the basic ways of glucose conversion to waxy starch in plants. The recent evidence of ADP-Glc accumulation in cytosol of photosynthetically competent cells proposes a more complex pathway of starch biosynthesis based on a tight interconnection of sucrose and starch metabolic pathways. Also many studies indicate the existence of different pathways for the sucrose-starch conversion process in heterotrophic organs of dicotyledonous and monocotyledonous plants. At least six classes of starch synthases (SS) have been recognised in plants including soluble SS1, SS2, SS3, SS4, SS5, and granule bound SS (GBSS), required for the synthesis of short and long chains of amylopectin, till now. As to amylose (not-present in waxy starches), GBSS is the only starch synthase isoform encoded by the waxy genes situated at independent loci.

Isolation, characterization, and expression analysis of starch synthase IIa cDNA from wheat (Triticum aestivum L.)

Genome ◽  
2000 ◽  
Vol 43 (5) ◽  
pp. 768-775 ◽  
Author(s):  
Ming Gao ◽  
Ravindra N Chibbar
Keyword(s):  
Recombinant Protein ◽  
Polyclonal Antibody ◽  
Sequence Similarity ◽  
Triticum Aestivum L ◽  
Biochemical Properties ◽  
Starch Biosynthesis ◽  
Starch Synthase ◽  
Cdna Clones ◽  
Wheat Endosperm ◽  
Starch Synthases

We characterized three near-full-length putative homoeologous cDNA (Ss2a-1, Ss2a-2, and Ss2a-3) in wheat endosperm most similar to the maize zSSIIa. Polypeptide sequences deduced from three Ss2a cDNA clones share a 95% overall sequence similarity, and may thus have similar biochemical properties and may make identical contributions to starch biosynthesis in wheat endosperm. The accumulation of RNA transcripts corresponding to three Ss2a genes in developing endosperm varies among three cultivars studied, but usually peaks in young endosperm at about 10 days post anthesis (DPA). The polyclonal antibody for the SSIIa-1 recombinant protein strongly reacted to three previously identified granule-bound starch synthases of 100 to 115 kDa. The polyclonal antibody for the granule-bound starch synthases strongly reacted to the SSIIa-1 recombinant protein. Sequences of the N-terminal and an internal peptide of these three granule-bound starch synthases match well with those of three predicted mature SSIIa polypeptides. These granule-bound starch synthases may therefore be SSIIa polypeptides. The antibodies also recognized a group of three polypeptides with the same gel mobility as the three granule-bound starch synthases, a polypeptide of 90 kDa, and a group of three polypeptides of about 80 to 82 kDa. Thus, the wheat SSIIa may exist in several functional forms in the stroma of amyloplasts.Key words: starch granule, granule-bound proteins, soluble starch synthase, homoeologous isoforms, starch biosynthesis.

scholarly journals Interplay Between the N-Terminal Domains of Arabidopsis Starch Synthase 3 Determines the Interaction of the Enzyme With the Starch Granule

2021 ◽  
Vol 12 ◽  
Author(s):  
Francisco M. Gámez-Arjona ◽  
Ángel Mérida
Keyword(s):  
Starch Granule ◽  
Coiled Coil ◽  
Terminal Region ◽  
Starch Synthase ◽  
Full Length ◽  
Localization Pattern ◽  
Binding Domains ◽  
Starch Synthases ◽  
Linear Chains

The elongation of the linear chains of starch is undertaken by starch synthases. class 3 of starch synthase (SS3) has a specific feature: a long N-terminal region containing starch binding domains (SBDs). In this work, we analyze in vivo the contribution of these domains to the localization pattern of the enzyme. For this purpose, we divided the N-terminal region of Arabidopsis SS3 in three domains: D1, D2, and D3 (each of which contains an SBD and a coiled-coil site). Our analyses indicate that the N-terminal region is sufficient to determine the same localization pattern observed with the full-length protein. D2 binds tightly the polypeptide to the polymer and it is necessary the contribution of D1 and D3 to avoid the polypeptide to be trapped in the growing polymer. The localization pattern of Arabidopsis SS3 appears to be the result of the counterbalanced action of the different domains present in its N-terminal region.

scholarly journals Competition between Granule Bound Starch Synthase and Starch Branching Enzyme in Starch Biosynthesis

Rice ◽  
2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Huaxin Han ◽  
Chuantian Yang ◽  
Jihui Zhu ◽  
Lixia Zhang ◽  
Yeming Bai ◽  
...  
Keyword(s):  
Functional Properties ◽  
Length Distribution ◽  
Soluble Starch ◽  
Starch Biosynthesis ◽  
Starch Synthase ◽  
Size Exclusion ◽  
Rice Starch ◽  
Rice Varieties ◽  
Chain Length Distribution ◽  
Granule Bound Starch Synthase

Abstract Background Starch branching enzymes (SBE) and granule-bound starch synthase (GBSS) are two important enzymes for starch biosynthesis. SBE mainly contributes to the formation of side branches, and GBSS mainly contributes for the synthesis of amylose molecules. However, there are still gaps in the understanding of possible interactions between SBE and GBSS. Results Nineteen natural rice varieties with amylose contents up to 28% were used. The molecular structure, in the form of the chain-length distribution (CLDs, the distribution of the number of monomer units in each branch) was measured after enzymatic debranching, using fluorophore-assisted carbohydrate electrophoresis for amylopectin and size- exclusion chromatography for amylose. The resulting distributions were fitted to two mathematical models based on the underlying biosynthetic processes, which express the CLDs in terms of parameters reflecting relevant enzyme activities. Conclusions Finding statistically valid correlations between the values of these parameters showed that GBSSI and SBEI compete for substrates during rice starch biosynthesis, and synthesis of amylose short chains involves several enzymes including GBSSI, SBE and SSS (soluble starch synthase). Since the amylose CLD is important for a number of functional properties such as digestion rate, this knowledge is potentially useful for developing varieties with improved functional properties.

scholarly journals A newly-identified inactive starch synthase simultaneously regulates starch synthesis and carbon allocation in storage roots of cassava (Manihot esculenta Crantz)

2020 ◽  
Author(s):  
Shutao He ◽  
Xiaomeng Hao ◽  
Shanshan Wang ◽  
Wenzhi Zhou ◽  
Qiuxiang Ma ◽  
...  
Keyword(s):  
Carbon Allocation ◽  
Protein Complexes ◽  
Starch Synthesis ◽  
Feedback Regulation ◽  
Starch Biosynthesis ◽  
Starch Synthase ◽  
Biosynthetic Enzymes ◽  
Storage Roots ◽  
Manihot Esculenta Crantz ◽  
Functional Analyses

AbstractStarch is a glucose polymer synthesized by green plants for energy storage, and is crucial for plant growth and reproduction. The biosynthesis of starch polysaccharides is mediated by members of the large starch synthase (SS) protein superfamily. Here, we report the functionality of a cassava SS that clusters with a previously unreported lineage, SSVI. A phylogenetic analysis based on SS sequences from 44 plant species showed that SSVI is distributed in eudicots, but not in monocots. Functional analyses showed that in cassava storage roots, SSVI is inactive but plays an important role in both starch biosynthesis and carbon allocation via sugar-induced feedback regulation and also by forming protein complexes with starch biosynthetic enzymes. Contrary to current dogma, our results show a close coordination between granule-bound starch synthase and amylopectin biosynthetic enzymes, which implies that the processes of amylose synthesis and amylopectin synthesis are directly interrelated. These findings shed light on the key components of the starch biosynthesis machinery in root crops.

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