Exterior Chain Length Research Articles

Effects of Four Non‐Synonymous SNPs of SSIIa Gene on Amylopectin Structure and Gelatinization Characteristics in Rice

AbstractSoluble starch synthase IIa gene (SSIIa) is one of the key genes involved in the synthesis of amylopectin and a major gene controlling the gelatinization temperature of rice. In this study, specific molecular markers are designed for the four functional SNPs of the SSIIa gene, namely 264 (SNP1), 1810 (SNP2), 2209 (SNP3), and 2340–2341 (SNP4). In addition, 91 rice varieties are tested and the correlation of these SNPs with the structure of amylopectin, RVA profile characteristics, and gelatinization temperature are also analyzed. The results show that SNP1 (C/G) and SNP2 (A/G) of the SSIIa gene are significantly associated with the A:B value, SBV, and gelatinization temperature. The SNP4 (GC/TT) is significantly associated with the gelatinization temperature. Among the four haplotypes, namely C‐A‐A‐GC (HP1), C‐A‐G‐TT (HP2), G‐G‐G‐GC (HP3), and C‐A‐G‐GC (HP4), HP1 varieties show shorter chain length (CL) and exterior chain length (ECL), HP3 show a lower A:B value, whereas HP3 and HP4 varieties show lower PKV, BDV, and higher CPV, SBV, gelatinization temperature. The results suggest that different nonsynonymous SNPs in SSIIa may alter the activity of the SSIIa enzyme and further affect the CL and ECL of amylopectin, resulting in a different RVA profile and gelatinization temperature of starch.

Study on crystalline, gelatinization and rheological properties of japonica rice flour as affected by starch fine structure

Although many researches have investigated the effects of starch characteristics on its functional properties to evaluate rice quality, few studies were carried out the correlations between starch molecular structure and rice processing properties. In this study, eight varieties of japonica rice with similar content of protein and lipid and less variant content of amylose (12.12–18.19%) were elaborately selected. The result showed that crystalline and pasting parameters were mainly reliant on the differences in chain length distribution of amylopectin. Amylose content and chain length distribution, especially for average exterior chain length (ECL) and interior chain length (ICL) and their entanglement, showed significant correlation on rheological parameters. Swelling power of rice flour showed negative correlation with amylose content. Furthermore, in temperature-reduction process when the temperature is lower gelatinization temperature of amylopectin, the variation of loss modulus was affected by amylopectin. In addition, the PCA plot clearly revealed the interrelationship of all parameters.

Structural and physicochemical characterisation of rye starch

The gelatinisation, pasting and retrogradation properties of three rye starches isolated using a proteinase-based procedure were investigated and compared to those of wheat starch isolated in a comparable way. On an average, the rye starch granules were larger than those of wheat starch. The former had very comparable gelatinisation temperatures and enthalpies, but slightly lower gelatinisation temperatures than wheat starch. Under standardised conditions, they retrograded to a lesser extent than wheat starch. The lower gelatinisation temperatures and tendencies of the rye starches to retrograde originated probably from their higher levels of short amylopectin (AP) chains [degree of polymerisation (DP) 6–12] and their lower levels of longer chains (DP 13–24) than observed for wheat starch. The rapid visco analysis differences in peak and end viscosities between the rye starches as well as between rye and wheat starches were at least partly attributable to differences in the levels of AP short chains and in average amylose molecular weight. The AP average chain lengths and exterior chain lengths were slightly lower for rye starches, while the interior chain lengths were slightly higher than those for wheat starch.

In vitro synthesis of glycogen: the structure, properties, and physiological function of enzymatically-synthesized glycogen

This review describes a new enzymatic method for in vitro glycogen synthesis and its structure and properties. In this method, short-chain amylose is used as the substrate for branching enzymes (BE, EC 2.4.1.18). Although a kidney bean BE and Bacillus cereus BE could not synthesize high-molecular weight glucan, BEs from 6 other bacterial sources produced enzymatically synthesized glycogen (ESG). The BE from Aquifex aeolicus was the most suitable for the production of glycogen with a weight-average molecular weight (Mw) of 3,000–30,000 k. The molecular weight of the ESG is controllable by changing the concentration of the substrate amylose. Furthermore, the addition of amylomaltase (AM, EC 2.4.1.25) significantly enhanced the efficiency of this process, and the yield of ESG reached approximately 65%. Typical preparations of ESG obtained by this method were subjected to structural analyses. The average chain length, interior chain length, and exterior chain length of the ESGs were 8.2–11.6, 2.0–3.3, and 4.2–7.6, respectively. Transmission electron microscopy and intrinsic viscosity measurement showed that the ESG molecules formed spherical particles. Unlike starch, the ESGs were barely degraded by pullulanase. Solutions of ESG were opalescent (milky-white and slightly bluish), and gave a reddishbrown color on the addition of iodine. These analyses revealed that ESG shares similar molecular shapes and solution properties with natural-source glycogen. Moreover, ESG had macrophage-stimulating activity and its activity depends on the molecular weight of ESG. We successfully achieved large scale production of ESG. ESG could lead to new industrial applications, such as in the food, chemical, and pharmaceutical fields.

Structure and solution properties of enzymatically synthesized glycogen

Recently, a new enzymatic process for glycogen production was developed. In this process, short-chain amylose is used as a substrate for branching enzymes (BE, EC 2.4.1.18). The molecular weight of the enzymatically synthesized glycogen (ESG) depends on the size and concentration of the substrate. Structural and physicochemical properties of ESG were compared to those of natural source glycogen (NSG). The average chain length, interior chain length, and exterior chain length of ESG were 8.2–11.6, 2.0–3.3, and 4.2–7.6, respectively. These values were within the range of variation of NSG. The appearances of both ESG and NSG in solution were opalescent (milky white and slightly bluish). Furthermore, transmission electron microscopy and atomic force microscopy showed that ESG molecules formed spherical particles, and that there were no differences between ESG and NSG. Viscometric analyses also showed the spherical nature of both glycogens. When ESG and NSG were treated with pullulanase, a glucan-hydrolyzing enzyme known to degrade glycogen only on its surface portion, both glycogens were similarly degraded. These analyses revealed that ESG shares similar molecular shapes and surface properties with NSG.

A New Method for in vitro Glycogen Synthesis, and the Structure and Properties of the Synthesized Glycogen

A new enzymatic process for glycogen production was developed. In this process, short-chain amylose is used as the substrate for branching enzymes (BE, EC 2.4.1.18). The molecular weight of the enzymatically synthesized glycogen (ESG) depends on the type of BE used and the molecular weight and the concentration of the substrate amylose. Although a plant BE (kidney bean) and Bacillus cereus BE could not synthesize high molecular weight glucan, BEs from 6 other bacterial sources produced ESG. The BE from Aquifex aeolicus was the most suitable for the production of glycogen with a weight-average molecular weight (Mw) of 3000 kDa to 30,000 kDa. Furthermore, the addition of amylomaltase (AM, EC 2.4.1.25) significantly enhanced the efficiency of this process, and the yield of ESG reached approximately 65%. Typical preparations of ESG obtained by this method were subjected to structural analyses. The average chain length, interior chain length, and exterior chain length of the ESGs were 8.2-11.6, 2.0-3.3 and 4.2-7.6, respectively. Transmission electron microscopy showed that the ESG molecules formed spherical particles. Viscometric analyses also supported a spherical nature for the product. Unlike starch, the ESGs were barely degraded by pullulanase. Solutions of ESG were opalescent (milky-white and slightly bluish), and gave a reddish-brown color on the addition of iodine. These analyses revealed that ESG shares similar molecular shapes and solution properties with natural source glycogen (NSG).

Underlying reasons for waxy rice flours having different pasting properties

The underlying reasons for three waxy rice varieties, Yang-fu-nuo (Y), Su-yu-nuo (S), and Guang-ling-xiang-nuo (G), having different flour pasting properties were examined. The pasting properties of the isolated waxy rice starches did not correlate with those of the corresponding waxy rice flours. Examining the pasting properties of the flours in 0.5 mM AgNO 3 solution, treated with dithiothreitol and protease, suggested that rice protein and amylase activity were the main causes of the pasting property differences among the rice starches and flours. Starch isolated from Y flour had a larger proportion of A and B 1 chains, longer average chain length and longer exterior chain length, which explained its higher gelatinisation temperature, higher pasting consistency, greater extent of retrogradation, and the firm texture of cooked Y rice.

Effect of Amylopectin Structure on the Gelatinization and Pasting Properties of Selected Yam (Dioscorea spp.) Starches

AbstractThis study was aimed at elucidating the decisive structural parameters of amylopectin which govern the gelatinization or pasting behavior of yam starch dispersions, exemplified with four selected yam starches from Dioscorea alata and D. batatas with very similar amylose contents (32.2–34.6%). The results indicated that the yam amylopectins examined showed an average degree of polymerization (DP) of 3469–4474 anhydroglucose units (AGU), average chain length (CL) of 18.8–28.5 AGU, average exterior CL (ECL) of 11.8–16.4 AGU, average interior CL (ICL) of 6.0–11.1 AGU, and a noticeable proportion of extralong (> 100 AGU) and long (40–100 AGU) chains that gave the chain ratio r(el+l)/s (the weight ratio of extralong and long chains to short chains) of 0.88–1.40. Generally, the yam amylopectin with a lower DP and NC possessed a greater CL, ECL, ICL, and r(el+l)/s, associating with a higher blue value (BV) and maximal wavelength (λmax) for their complexes with iodine. D. alata amylopectins exhibited a lower DP, longer chain lengths and greater r(el+l)/s than the D. batata amylopectins. Statistically, r(el+l)/s was decisive for the BV and λmax; while CL and phosphate content were crucial for the gelatinization peak temperature and pasting viscosities of the yam starches examined. The role of swelling power or the volume fraction of dispersed remnants instead in governing the pasting viscosity was also mathematically explored.

Changing the Amylopectin-Sodium Dodecyl Sulphate Interaction by Modifying the Exterior Chain Length

The retrogradation of amylopectin and its interaction with the surfactant sodium dodecyl sulphate (SDS) as a function of the exterior chain length (ECL) of the amylopectin molecules was investigated. Amylopectin was modified by partial beta-amylolysis, which decreased ECL without causing any other changes in the molecular structure. Retrogradation of amylopectin was studied with differential scanning calorimetry (DSC), in the presence and absence of SDS. The retrogradation enthalpy of amylopectin was significantly dependent on the ECL, whereas the melting temperature was only to some extent influenced by ECL. The ability of SDS to inhibit the retrogradation of amylopectin depended on ECL, which suggests that there was a specific binding of SIDS to amylopectin, The decrease in retrogradation when SDS was added to the amylopectin sample was less when ECL decreased. The overall effect was thus an increase in retrogradation in the presence of SIDS when the ECL decreased, Small changes in the molecular structure of amylopectin gave rise to sharp changes in both retrogradation and interaction with lipids, showing that the molecular structure is important for the crystallisation and interaction behaviour of amylopectin.

Structures of Four Waxy Rice Starches in Relation to Thermal, Pasting, and Textural Properties

ABSTRACTWaxy rice starches from three japonica cultivars (Taichung Waxy 1 [TCW1], Taichung Waxy 70 [TCW70], Tachimemochi) and one indica cultivar (Tainung Sen Waxy 2 [TNSW2]) were characterized for chemical and physicochemical properties. The amylopectin structures were different for the four waxy rice starches in terms of degree of polymerization (DP), average chain length (CL), exterior chain lengths (ECL), and distribution of chains, indicating the existence of varietal differences. The order of swelling power was TCW1 > TCW70 > TNSW2 > Tachimemochi; the order of water solubility index was TCW70 > TNSW2 > Tachimemochi > TCW1. The low water solubility index of TCW1 might be ascribed to a high DP. All starches shared similar gelatinization temperatures and enthalpies but showed distinct retrogradation patterns. TNSW2 showed the highest retrogradation rate, followed by TCW2, Tachimemochi, and TCW70. TCW70 exhibited the highest overall pasting viscosity, followed by TNSW2, TCW1, and Tachimemochi. The hardness of waxy rice starch pastes from a Brabender amyloviscograph increased rapidly after storage at 5°C for one day and remained the same or slightly increased after seven days of storage, whereas the opposite trend was observed for adhesiveness. The lower degree of retrogradation of TCW70 was probably a result of a larger amount of A chain and a shorter ECL. The changes in hardness correlated with the amount of A and B1 chains. The texture attributes of waxy rice starch pastes were significantly affected by amylopectin retrogradation during storage.

Molecular and Gelatinization Properties of Rice Starches from IR24 and Sinandomeng Cultivars

ABSTRACTThe differences in pasting properties involving gelatinization and retrogradation of rice starches from IR24 and Sinandomeng cultivars during heating‐cooling processes were investigated using a Rapid Visco Analyser (RVA)and a dynamic rheometer. The results were discussed in relation to the molecular structure, actual amylose content (AC), and concentration of the starches. Generally, both starches possessed a comparable AC (≈11 wt%), amylose average chain length (CL), iodine absorption properties, and dynamic rheological parameters on heating to 95°C at 10 wt% and on cooling to 10°C at higher concentrations. In contrast to Sinandomeng, IR24 amylose had a greater proportion of high molecular weight species and number‐average degree of polymerization (DPn). IR24 amylopectin possessed a lower DPn and greater CL, exterior CL (ECL), and interior CL (ICL). Comparing the results of RVA analysis and dynamic rheology, the gelatinization properties and higher retrogradation tendencies of IR24 starch can be related to the structural properties and depend on starch concentration. In addition, the exponent n of starch concentration for storage moduli at 25°C (G′25 ∝ Cn) increased linearly with increasing AC.

Kinetic properties of glycogen synthase and phosphorylase and structural aspects of glycogen in the db/db mouse liver.

Kinetic studies were carried out on liver glycogen synthase and phosphorylase isolated from genetically diabetic db/db mice. Glycogen synthase a and b enzymes from diabetic mice had Vmax values 30% and 20% lower, respectively, than the enzymes from normal mice. Glycogen synthase b from diabetic mice also had a 30% lower I0.5 for Pi and ATP at physiologic concentrations of UDP-glucose (0.25 mM) compared with the normal enzyme. Kinetic studies of phosphorylase a showed that, at low glycogen concentrations (0.25 mg/ml), the Vmax of the diabetic enzyme was twofold greater than that of the normal enzyme. This was probably related to the diabetic phosphorylase a having a lower apparent Km for glycogen. This enzyme also had a slightly higher I0.5 for ATP compared with the enzyme from normal mice. Structural studies of liver glycogen isolated from these diabetic mice showed differences from normal mouse glycogen. Both the alpha- and beta-amylase limits were lower in the diabetic glycogen, and the average chain lengths, exterior chain lengths, and interior chain lengths calculated from these limits were all shorter in the glycogen from diabetic mice. Although both normal and diabetic glycogen absorbed light maximally at 430 nm when complexed with iodine, the absolute absorbance value was significantly lower for the diabetic glycogen. These data suggest an altered branching pattern of liver glycogen from the diabetic mice and it is suggested that this altered structure may ultimately influence the activities of glycogen-metabolizing enzymes. These results provide further characterization of the db/db mouse and show heretofore undescribed changes in phosphorylase a kinetics and glycogen structure that occur in diabetes.

Variation in the degree of branching of the glycogens and an approximate relationship between average exterior chain length and iodine staining

AbstractPrecise evaluation of the branching characteristics of glycogen complex from a variety of sources was made by replicate determinations of end groups by a reproducible periodate oxidation method and by replicate determinations of the percentage degradation by exhaustive β‐amylase activity. Also, the iodine staining characteristics of these samples were studied. The following observations were made. During the synthesis of glycogen by baker's yeast, there was a significant increase in the average chain length of the glycogen, and the maximal optical absorbance AM of the glycogen–iodine complex doubled. The AM decreased linearly with increasing temperature, and increases in iodine concentration caused increases in both the AM and the wavelength of maximal absorbance. There was a general increase in the AM of the glycogen with increasing exterior chain length, but there were minor deviations due to some dependence on the source of the glycogen. Unlike the linear relationship between the AM per chain and the average chain length of the amyloses, the AM per chain was exponentially related to the average exterior chain length of the glycogens.

The occurrence and identification of intracellular polyglucose storage granules in Methylococcus NCIB 11083 grown in chemostat culture on methane.

The accumulation of intracellular storage granules (0.03--0.5 micrometer) by Methylococcus NCIB 11083 when grown under conditions of ammonia limitation with methane as the sole source of carbon and energy was inversely proportional to the dilution rate. The isolated material was composed entirely of glucose residues and the infra-red spectrum exhibited characteristic absorption bands at 925 cm(-1), 845 cm(-1) and 745 +/- 4cm(-1), indicating the presence of alpha (1 leads to 4) glycosidic linkages. The polymer dissolved in hot water to give an opalescent solution that formed a violet iodine complex with an absorption maximum at 550nm, identical to that observed with reference amylopectin. The percentage of the polysaccharide released as maltose by the action of beta- and alpha-amylases was 55--64% and 80--90% respectively, values very similar to those obtained by the action of these enzymes on reference amylopectin and glycogen. Methylation analysis indicated that the average interior and exterior chain lengths of the polymer were 2.7 and 10.0 glucose units respectively and confirmed that the Methylococcus polyglucose is a branched polymer composed of units joined by 1 leads to 4 and 1 leads to 6 linkages. The number average molecular weight of the polymer is 2--4.5 x 10(5). The stored polymer was metabolised by the organism and its metabolism resulted in the synthesis of protein.

Isolation and characterization of glycogen from Streptococcus salivarius.

Highly purified glycogen was isolated and characterized from the oral microbe Streptococcus salivarius. The wavelength for the maximum absorption of the iodine complex, the specific optical rotation, along with the values for the average chain length, exterior chain length, and interior chain length, were within the range reported for other microbial and animal glycogens.

α-1,4-GLUCANS. PART XX. THE MOLECULAR STRUCTURE OF THE STARCHES FROM OATS AND MALTED OATS*

Starch was isolated from samples of oats and malted oats, and fractionated into amylose and amylopectin components. Analysis showed that malting caused a very limited decrease in the molecular size of the amylose, and a small but significant reduction in the exterior chain length of the amylopectin. These changes are very similar to those which occur when oat starch granules are subjected to limited α-amylolysis. It is suggested that α-amylase is the predominant enzyme involved in the changes which occur in cereal starches during malting.