Thermal Characteristics of Soluble Starch Synthase From Wheat Endosperm

1995 ◽  
Vol 22 (4) ◽  
pp. 703 ◽  
Author(s):  
CF Jenner ◽  
K Denyer ◽  
J Guerin
Keyword(s):  
Thermal Characteristics ◽  
Soluble Starch ◽  
Starch Synthase ◽  
Wheat Grain ◽  
Wheat Endosperm ◽  
Temperature Range ◽  
Higher Temperature ◽  
Temperature Responses

The aim of the work reported in this paper was to characterise the thermal responses of soluble starch synthase (SSS) extracted from the endosperm of the developing wheat grain. Using partially purified preparations of SSS, the reaction obeyed Michaelis-Menten kinetics with both substrates amylopectin and ADPglucose. Both the Vmax and the Km varied with temperature. Values for Vmax were higher at 45�C compared with 25�C. However, the Km values for both substrates were also higher at 45�C than at 25�C indicating that the affinity of the enzyme for its substrates was reduced at the higher temperature. Over the temperature range 15-45�C, the Km for arnylopectin was minimal at 20�C, and rose exponentially between 25 and 45�C. Kinetic analyses indicated that the reaction was sequential and that the substrates could bind to the enzyme in either order. At 25�C the binding of one substrate to the enzyme increased the affinity of the complex for the second substrate but at 45�C these effects were abolished. These thermal characteristics of SSS could explain certain important features of the temperature responses of starch deposition in the wheat grain in vivo.

Starch Synthesis in the Kernel of Wheat Under High Temperature Conditions

1994 ◽  
Vol 21 (6) ◽  
pp. 791 ◽  
Author(s):  
CF Jenner
Keyword(s):  
High Temperature ◽  
Dry Matter ◽  
Starch Content ◽  
Starch Synthesis ◽  
Temperature Response ◽  
Grain Filling ◽  
Soluble Starch ◽  
Grain Weight ◽  
Temperature Range ◽  
Temperature Responses

As temperature rises above 18-22�C, the observed decrease in the duration of deposition of dry matter in the kernel is not accompanied by a compensating increase in the rate of grain filling with the result that grain weight (and yield) is diminished at high temperature. Reduced starch content accounts for most of the reduction in grain dry matter at high temperature. Responses to temperature in the low temperature range, 20-30�C (the LTR), could possibly be ascribed to the temperature response characteristics of the reaction catalysed by soluble starch synthase (SSS), the enzyme synthesising starch. However, the rate of cell enlargement and the rate of accumulation of nitrogen in the grain also do not increase much as temperature rises, so other explanations are conceivable for the temperature responses in the LTR. Variation amongst cultivars of wheat in tolerance of high temperature is evident in the LTR. At temperatures above 30�C (in the high temperature range (HTR) between 30 and 40�C), even for short periods, the rate of starch deposition is slower than that observed at lower temperatures, an effect which is carried over after transfer from high to lower temperatures. This response is attributable to a reduction in the activity, possibly due to thermal denaturation, of SSS. Several forms of SSS are found in cereal endosperm, and some forms may be more tolerant of high temperature than others. Loss of enzyme activity at high temperature is swift, but is partly restored some time after transfer from hot to cool conditions. There appear to be two distinct mechanisms of response to elevated temperature, both resulting in a reduced grain weight through reduced starch deposition, but one of them is important only in the range of temperature above 30�C.

Effects of high temperature on grain growth and on the metabolites and enzymes in the starch-synthesis pathway in the grains of two wheat cultivars differing in their responses to temperature

2003 ◽  
Vol 30 (3) ◽  
pp. 291 ◽  
Author(s):  
Morteza Zahedi ◽  
Rajinder Sharma ◽  
Colin F. Jenner
Keyword(s):  
High Temperature ◽  
Starch Synthesis ◽  
Grain Filling ◽  
Triticum Aestivum L ◽  
Soluble Starch ◽  
Starch Synthase ◽  
Effect Of Temperature ◽  
The Difference

The effects of a sustained period of moderately high temperature were evaluated on the availability of substrate and the activity of starch synthase (ADP-glucose: 1,4-α-D-glucan 4-α-D-glucosyltransferase, EC 2.4.1.21) in the developing grains of two wheat Triticum aestivum L. cultivars differing in their tolerance to high temperature. Final grain weight was reduced by 33% in the least sensitive (cv. Kavko) and by 40% in the most sensitive (cv. Lyallpur) cultivar as post-anthesis temperature was raised from 20/15°C (day/night) to 30/25°C. The difference in the response of the two cultivars was mainly due to changes in the rate of grain filling at high temperature. The response of the rate of grain filling at high temperature, and the differential effects on the two cultivars, did not seem to be explained by an effect of temperature on the supply of assimilate (sucrose) or on the availability of the substrate for starch synthesis (ADP-glucose) in the grains. In vitro, but not in vivo, the differential responses of the efficiency (Vmax/Km) of soluble starch synthase in the two cultivars to an increase in temperature were associated with differences in the temperature sensitivity of grain filling. In vivo, the most remarkable difference between the two varieties was in the absolute values of the efficiency of soluble starch synthase, with the most tolerant cultivar having the highest efficiency.

Thermal Characteristics of Damp Hydrophobic, Microfibrous Batt

1988 ◽  
Vol 110 (1) ◽  
pp. 19-22
Author(s):  
K. A. Steele
Keyword(s):  
Thermal Conductivity ◽  
Mathematical Model ◽  
Thermal Characteristics ◽  
Region Of Interest ◽  
Experimental Results ◽  
Preliminary Design ◽  
Insulating Material ◽  
Temperature Range ◽  
Higher Temperature ◽  
Thermal Conductivities

The thermal characteristics of damp, hydrophobic insulating material used primarily in underwater dry suit applications were investigated. Testing was performed in a Rapid-K Thermal Conductivity Instrument manufactured by Dynatech, Inc. A mathematical model of the process was proposed, and the results obtained using this model were compared to experimental results. The two agreed well except in the higher temperature range, where the model predicts higher thermal conductivities than those observed. However, for the region of interest agreement was good, and the model should be considered valid for the preliminary design of dry suits using hydrophobic batting as an insulator.

scholarly journals Genetic Effects of Soluble Starch Synthase IV-2 and It with ADPglucose Pyrophorylase Large Unit and Pullulanase on Rice Qualities

2020 ◽  
Author(s):  
Liang Xu ◽  
Hui You ◽  
Ouling Zhang ◽  
Xunchao Xiang
Keyword(s):  
Amylose Content ◽  
Starch Synthesis ◽  
Thermal Characteristics ◽  
Soluble Starch ◽  
Starch Synthase ◽  
Peak Time ◽  
Major Genes ◽  
Rice Quality ◽  
Large Unit ◽  
Apparent Amylose Content

Abstract Background: Rice amylose content and amylopectin structure corporately determine rice eating and cooking qualities (ECQs). Soluble starch synthase ( SS ) IV-2 is a member of the soluble starch synthesis gene family but with unknown effects on ECQs. Results: In this study, three populations derived from a cross of two parents who possess the same major genes of starch bio-synthesis were employed to investigate the influence of SSIV-2 and its combined effects with ADPglucose pyrophorylase large unit ( AGPlar ) and Pullulanase ( PUL ) on ECQs. The results illustrated that the polymorphism of SSIV-2 alleles significantly affected gel consistency (GC), gelatinization temperature (GT), percent of retrogradation (PR) and three crucial rapid viscosity analysis (RVA) profile parameters: peak viscosity (PKV), breakdown viscosity (BDV) and setback viscosity (SBV). And SSIV-2 allele derived from CG173R had better quality traits with lower GT, SBV and PR. Moreover, its interaction with AGPlar was responsible for the variations of GC, apparent amylose content (AAC), GT, PR and all RVA parameters except for pasting temperature (PaT) and peak time (PeT), in terms of GC, PKV and CSV, AGPlar derived from CG173R had an epistatic effect on SSIV-2 ; additionally, interaction of SSIV-2 and PUL mainly affected GC, AAC, PKV, CPV, CSV and SBV. I-C and C-1 (I, allele of AGPlar from Guangzhan 63S; C, allele of SSIV-2 from CG173R; 1, allele of PUL from Guangzhan 63S) combinations had better ECQs. Conclusions: SSIV-2 alleles significantly affect rice quality, especially the parameters relevant to gelatinized and thermal characteristics of starch (GC, PR, GT, PKV, BDV and SBV) under the same major genes ( Waxy and SSII-3 ) background. It indicates that SSIV-2 functions elongation of starch chain. These findings suggest that the effects of SSIV-2 and its interaction with AGPlar and PUL are vital for rice quality breeding with the same major genes.

scholarly journals Toward an understanding of the biogenesis of the starch granule. Determination of granule-bound and soluble starch synthase functions in amylopectin synthesis.

1994 ◽  
Vol 269 (40) ◽  
pp. 25150-25157
Author(s):  
M.L. Maddelein ◽  
N. Libessart ◽  
F. Bellanger ◽  
B. Delrue ◽  
C. D'Hulst ◽  
...  
Keyword(s):  
Starch Granule ◽  
Soluble Starch ◽  
Starch Synthase

scholarly journals QTL-seq identifies cooked grain elongation QTLs near soluble starch synthase and starch branching enzymes in rice (Oryza sativa L.)

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Siwaret Arikit ◽  
Samart Wanchana ◽  
Srisawat Khanthong ◽  
Chatree Saensuk ◽  
Tripop Thianthavon ◽  
...  
Keyword(s):  
Oryza Sativa ◽  
Oryza Sativa L ◽  
Soluble Starch ◽  
Starch Synthase ◽  
Starch Branching Enzymes ◽  
Branching Enzymes

scholarly journals Synthesis and characterization of PIL/pNIPAAm hybrid hydrogels

2016 ◽  
Vol 2 (1) ◽  
pp. 1-4
Author(s):  
Sylvia Pfensig ◽  
Daniela Arbeiter ◽  
Klaus-Peter Schmitz ◽  
Niels Grabow ◽  
Thomas Eickner ◽  
...  
Keyword(s):  
Mechanical Characterization ◽  
Heating Temperature ◽  
Controlled Drug Release ◽  
Solution Temperature ◽  
Scanning Calorimetry ◽  
Critical Solution Temperature ◽  
Temperature Range ◽  
Hybrid Hydrogels ◽  
Higher Temperature

AbstractIn this study, varying amounts of NIPAAm and an ionic liquid (IL), namely 1-vinyl-3-isopropylimidazolium bromide ([ViPrIm]+[Br]−), have been used to synthesize hybrid hydrogels by radical emulsion polymerization. Amounts of 70/30%, 50/50%, 30/70%, 15/85% and 5/95% (wt/wt) of PIL/pNIPAAm were used to produce hybrid hydrogels as well as the parental hydrogels. The adhesive strength was investigated and evaluated for mechanical characterization. Thermal properties of resulting hydrogels have been investigated using differential scanning calorimetry (DSC) in a default heating temperature range (heating rate 10 K min−1). The presence of poly ionic liquids (PIL) in the polymer matrix leads to a moved LCST (lower critical solution temperature) to a higher temperature range for certain hybrid hydrogels PIL/pNIPAAm. While pNIPAAm exhibits an LCST at 33.9 ± 0.3°C, PIL/pNIPAAm 5/95% and PIL/pNIPAAm 15/85% were found to have LCSTs at 37.6 ± 0.9°C and 52 ± 2°C, respectively. This could be used for controlled drug release that goes along with increasing body temperature in response to an implantation caused infection.

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