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Grass pollen allergens
Published in Richard F. Lockey, Dennis K. Ledford, Allergens and Allergen Immunotherapy, 2020
A characteristic of the group 5 allergens is their association with intracellular starch granules within the pollen grain. The cDNA sequence of Lol p 5 revealed the flanking transit peptide sequences typical of chloroplast-targeted proteins; thus, it was proposed that the Lol p 5 is synthesized as a preallergen in the cytosol and transported to the amyloplast for posttranslational modification [100]. This model may explain the existence of the multiple isoforms and the molecular weight heterogeneity of group 5 allergens isolated from pollen extracts. The size of the starch granules (0.6–2.5 μm in diameter) and their sudden appearance in air samples following rainfall are suggestive of a role in triggering asthmatic reactions. Ph1 p 5 possesses ribonuclease activity, and the homologous group 5 allergens from the other grass species may be expected to possess this activity as well [101]. It is interesting to speculate on the role of ribonuclease activity at the level of pollen-stigma interaction: Its release during hydration and stigma contact might facilitate the reproductive responses of the stigma.
Legume Nodule Biochemistry and Function
Published in Peter M. Gresshoff, Molecular Biology of Symbiotic Nitrogen Fixation, 2018
Robert B. Mellor, Dietrich Werner
After the conversion of sucrose to glucose-6-phosphate, some of the carbon is drawn to a separate pool to deposit starch in amyloplasts. This pool presumably acts as a buffer to cover energy needs during diurnal rhythm or stress periods, since N2 fixation continues for some days after photosynthate cutoff to mature nodules.8
Cassava toxicity, detoxification and its food applications: a review
Published in Toxin Reviews, 2021
Anil Panghal, Claudia Munezero, Paras Sharma, Navnidhi Chhikara
In cassava, majority of the starch is stored within amyloplasts in the thickened root. The starch content in roots varies from 73.7% to 84.9% on dry weight basis (Asaoka et al.1991). Amylose varies from 13.6 to 23.8% and amylopectin is about 83%. The content of soluble amylose (which is thought to be responsible for cohesiveness in cooked starch) of cassava was found in range from 10 to 40% of total amylose. Water absorption capacity and swelling power of starch are essential parameter for its viscosity and textural attributes in finished product. Cassava starch has good potential as food industry base product due to its high viscosity, low tendency for retrogradation, low gelatinization temperature, and also the absence of the undesirable flavors found in many cereal starches (Demiate and Kotovicz 2011). The starch obtained from fresh roots is having more swelling power than the one obtained from dried roots, therefore have better textural and viscosity attributes of finished products (Zhu 2015). Moreno and Gourdji (2015) reported that high rainfall leading to humid conditions results in sprouting causing the translocation of photoassimilates from the roots to the top and thus declining both dry matter and starch content of the roots.
Resistant starch, microbiome, and precision modulation
Published in Gut Microbes, 2021
Peter A. Dobranowski, Alain Stintzi
Starch is synthesized in the amyloplast and chloroplast organelles of plants, forming mixtures of amylose and amylopectin. These molecules both consist of chains of glucose subunits linked by α-1,4- and α-1,6-glycosidic bonds, but differ in their chain length (i.e. degree of polymerization; DP) and branching (α-1,6 bonds). Amylose possesses a DP below 6,300 glucose subunits, almost entirely (>99.3%) bonded by α-1,4-glycosidic linkages.16 Conversely, amylopectin forms much larger molecules (DP up to 26,500) with dense networks of short chains (mean DP 15–18) branching from longer chains (mean DP 48 to 60).16 The intra- and intermolecular interactions of amylose and amylopectin impart starch granules with a complex hierarchical structure (Figure 1).