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1.
Several methodologies have been developed for cereal amylolytic activity estimation, but there is lack of information about the application of these methods for fruits. Mature green banana fruit can achieve 20% of starch content which is degraded during the ripening period in a complex process involving alpha- and beta-amylases and alpha-1,4 and alpha-1,6-glucosidases, besides phosphorylases that can compete for the same substrates. Methods used to determine total hydrolytic activity and individual activity of enzymes involved in starch breakdown were compared for banana extracts in several ripening stages. Total hydrolytic activity was measured by DNS and iodometric methods. Endoamylolytic activity on amylose-azure substrate was also evaluated. BPNPG7 and PNPG5 chromogenic substrates were used for alpha- and beta-amylase activities, respectively. The results showed that methods that depend on the use of thermal treatment or on inhibitors to inactivate one of the enzymes were not adequate. The use of p-nitrophenol derivatives seemed to be the most specific, reproducible, and easiest method employed for single alpha- and beta-amylases activities determination in complex tissues. The DNS and iodometric methods can be used only for initial screenings of total hydrolytic activity, because the nonspecific substrate used in these procedures allows the action of more than one enzyme simultaneously.  相似文献   

2.
Alpha-amylases (EC 3.2.1.1) are glycosyl hydrolases with endoglycolytic activity on the alpha-1,4-d-glucosidic linkages in starch. In bananas, the mobilization of starch accounts for sugar accumulation during ripening, and among several hydrolytic enzymes, alpha-amylase is the only enzyme argued to be able to attack the intact granules, indicating a pivotal role for this enzyme. A 1953 bp full-length banana alpha-amylase cDNA (MAmy), encoded for a sequence of 416 amino acids, was cloned and used for heterologous expression in Pichia pastoris. The cloned MAmy presented the highly conserved motifs common to alpha-amylases, and the amylolytic activity of the extracts from yeast transformed with MAmy demonstrated that it encodes for a functional alpha-amylase, suggesting a putative role for this gene in starch degradation during fruit ripening.  相似文献   

3.
Different banana cultivars were used to investigate the influences of starch granule structure and hydrolases on degradation. The highest degrees of starch degradation were observed in dessert bananas during ripening. Scanning electron microscopy images revealed smooth granule surface in the green stage in all cultivars, except for Mysore. The small and round granules were preferentially degraded in all of the cultivars. Terra demonstrated a higher degree of crystallinity and a short amylopectin chain length distribution, resulting in high starch content in the ripe stage. Amylose content and the crystallinity index were more strongly correlated than the distribution of amylopectin branch chain lengths in banana starches. α- and β-amylase activities were found in both forms, soluble in the pulp and associated with the starch granule. Starch-phosphorylase was not found in Mysore. On the basis of the profile of α-amylase in vitro digestion and the structural characteristics, it could be concluded that the starch of plantains has an arrangement of granules more resistant to enzymes than the starch of dessert bananas.  相似文献   

4.
苏旺  胡禄华  王舰 《核农学报》2021,35(3):737-744
为探讨垄沟集雨覆盖栽培对旱作马铃薯块茎形成过程中淀粉合成关键酶活性、基因表达及淀粉累积的影响,以马铃薯栽培品种青薯9号为材料,设置全膜双垄和地膜垄作覆盖栽培模式,以露地平播为对照,测定马铃薯块茎形成过程中淀粉合成关键酶活性、基因表达及淀粉累积指标。结果表明,从块茎发育全过程来看,全膜双垄和地膜垄作覆盖栽培马铃薯可溶性淀粉合成酶(SSS)活性分别较露地平播显著提高77.70%、22.63%,可溶性淀粉合成酶SSIII基因表达量分别较露地平播显著提高32.26%、119.35%,同时,ADP-葡萄糖焦磷酸化酶(AGPP)、颗粒结合型淀粉合成酶(GBSS)活性和ADP-葡萄糖焦磷酸化酶AGPase、可溶性淀粉合成酶SSII、颗粒结合型淀粉合成酶GBSSI、淀粉分支酶SBEI、淀粉分支酶SBEII基因表达量均明显降低,而淀粉分支酶(SBE)活性无显著变化;全膜双垄覆盖栽培马铃薯总淀粉含量、直链淀粉含量及直/支链淀粉比较露地平播分别提高5.04%、17.57%和27.81%,达到显著水平,而地膜垄作明显降低了马铃薯总淀粉含量、直链淀粉含量及直/支链淀粉比;SSS活性与GBSSI基因表达量呈显著负相关,与直链淀粉含量及直/支链淀粉比呈显著正相关,其他淀粉合成关键酶活性均与基因表达量、淀粉累积指标无明显相关性。本研究结果对筛选青海东部旱区马铃薯适宜的淀粉优质生产措施具有重要意义。  相似文献   

5.
During mango ripening, soluble sugars that account for mango sweetening are accumulated through carbon supplied by both photosynthesis and starch degradation. The cultivar Keitt has a characteristic dependence on sugar accumulation during starch degradation, which takes place during ripening, only a few days after detachment from the tree. Most knowledge about starch degradation is based on seeds and leaves currently used as models. However, information about the mango fruit is scarce. This work presents the evaluation of alpha- and beta-amylases in the starch granule surface during fruit development and ripening. Extractable proteins were assayed for amylase activity and detected by immunofluorescence microscopy and correlated to gene expression. The results suggest that both amylases are involved in starch degradation during mango ripening, probably under the dependence of another signal triggered by the detachment from the mother-plant.  相似文献   

6.
吴佳瑞  康建宏  柳强娟  慕宇  孙建波  吴娜 《核农学报》2019,33(12):2482-2491
为探明宁南半干旱雨养农业区马铃薯块茎中淀粉和关键酶活性对黑色地覆盖膜的响应机理,在2016年和2017年以宁南山区马铃薯主栽品种青薯9号为材料,通过两年大田试验,研究了黑膜覆盖(BF)、白膜覆盖(WF)和不覆膜(NF)对马铃薯块茎中淀粉及其组分积累、淀粉合成关键酶活性的影响。结果表明,与WF和NF相比,BF的直链淀粉、支链淀粉、总淀粉含量分别增加11.37%~35.68%、8.56%~27.05%、8.33%~27.60%,淀粉积累速率提高13.80%~37.90%;BF、WF、NF条件下块茎ADPG焦磷酸化酶(AGPase)、UDPG焦磷酸化酶(UGPase)、淀粉分支酶(SBE)、可溶性淀粉合酶(SSS)、束缚态淀粉合酶(GBSS)活性均呈单峰曲线变化,BF的淀粉合成关键酶活性明显高于WF和NF。与WF和NF相比,BF的AGPase活性分别增加12.81%和40.24%;UGPase活性分别增加15.34%和36.52%、SBE活性分别增加16.64%和44.17%、SSS活性分别增加13.69%和34.76%、GBSS活性分别增加15.75%和45.44%。BF产量较WF和NF分别提高14.54%和57.23%。相关分析表明,马铃薯块茎中直链淀粉、支链淀粉和总淀粉含量与AGPase、UGPase、SBE、SSS、GBSS活性在多数测定时期呈正相关(P<0.01)。因此,在干旱半干旱地区采用黑色地膜覆盖栽培能够通过影响淀粉合成关键酶,进而提高马铃薯块茎中的淀粉及其组分含量,最终影响马铃薯的产量。  相似文献   

7.
Manipulation of starch composition in cereals and particularly in wheat is receiving increasing attention due to recognition of its important role in food and nonfood applications. The amylose/ amylopectin ratio influences the physicochemical properties of starches and nutritional value of derived end products. Identification of the key enzymes involved in the starch biosynthetic pathway has opened new avenues for altering the amylose and amylopectin content in durum and bread wheat. The granule bound starch synthases (GBSSI), or waxy proteins, are the enzymes responsible for amylose synthesis in storage tissues; amylopectin is produced by the concerted action of different enzymes, including starch synthases (SS), branching (SBE), and debranching enzymes (DBE). By altering the level of key enzymes involved in the regulation of starch synthesis, it is possible to generate novel starches with unique functional properties. In this respect, both low and high amylose starches are particularly interesting because they are associated with industrial and processing properties as well as with human health and nutrition. So far, major attention has addressed the manipulation of starch composition in bread wheat, whereas durum wheat has been investigated to a much lesser extent. Approaches currently available to alter amylose/amylopectin ratio and tailor starch composition in durum wheat are presented.  相似文献   

8.
Starch phosphorylases are enzymes that can use starch as substrate, and they are supposed to act in both in starch synthesis and degradation. This paper reports the effects of ethylene and 1-methylcyclopropene (1-MCP) on the degradation of starch and phosphorylase activity and gene expression. The results indicate that phosphorylase activity is induced during ripening and that it is associated with the onset of starch degradation. The regulation of banana phosphorylase activity is mainly dependent on gene expression, and the absence of ethylene perception by 1-MCP had a positive effect. However, this effect can be precluded by increased levels of ethylene, both autocatalytic and exogenous.  相似文献   

9.
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10.
Maltooligosyltrehalose synthase (MTSase) is one of the key enzymes involved in trehalose production from starch and catalyzes an intramolecular transglycosylation reaction by converting the alpha-1,4- to alpha,alpha-1,1-glucosidic linkage. Mutations at residues F206, F207, and F405 were constructed to change the selectivity of the enzyme because the changes in selectivity could reduce the side hydrolysis reaction of releasing glucose and thus increase trehalose production from starch. As compared with wild-type MTSase, F405Y and F405M MTSases had decreased ratios of the initial rate of glucose formation to that of trehalose formation in starch digestion at 75 degrees C when wild-type and mutant MTSases were, respectively, used with isoamylase and maltooligosyltrehalose trehalohydrolase (MTHase). The highest trehalose yield from starch digestion was by the mutant MTSase having the lowest initial rate of glucose formation to trehalose formation, and this predicted high trehalose yield better than the ratio of catalytic efficiency for hydrolysis to that for transglycosylation.  相似文献   

11.
The starches were separated from unripe apples of five cultivars (Criterion, Ruspippum, Red Spur, Skyline Supreme, and Granny Smith) and evaluated using scanning electron microscopy (SEM), gel permeation chromatography (GPC), X-ray diffraction, differential scanning calorimetry (DSC), and dynamic viscoelasticity. SEM showed the presence of round granules as well as granules that had been partially degraded, probably by amylases. The starch granules in different apple starches ranged between 4.1 and 12.0 mum. Debranching of starch with isoamylase and subsequent fractionation of debranched materials by GPC revealed the presence of an apparent amylose, an intermediate fraction (mixture of amylose and amylopectin), long side chains of amylopectin, and short side chains of amylopectin in the range of 28-35.2, 3.6-4.4, 20-21.3, and 39.9-47.1%, respectively. The swelling power of starches ranged between 14.4 and 21.3 g/g. X-ray diffraction of apple starches showed a mixture of A- and B-type patterns. All apple starches showed peak intensities lower than that observed for normal corn and potato starch, indicating the lower crystallinity. The transition temperatures (onset temperature, T(o); peak temperature, T(p); and conclusion temperature, T(c)) and enthalpy of gelatinization (deltaH(gel)) determined using DSC ranged between 54.7 and 56.2 degrees C, between 57.1 and 59.1 degrees C, between 60.2 and 63.5 degrees C, and between 3.3 and 4.2 J/g, respectively. The viscoelastic properties of starch from different cultivars measured during heating and cooling using a rheometer differed significantly. Red Spur and Criterion starches with larger granule size showed higher G' and G' ' values, whereas those containing smaller size and amylolytically degraded granules showed lower G' and G' '.  相似文献   

12.
One novel banana fruit ripening related 1-aminocyclopropane-1-carboxylate (ACC) oxidase gene quite different from ACC oxidase genes from other species was cloned. In contrast to other studies, the polypeptide encoded by this gene, named Mh-ACO1, lacks the putative leucine zipper motif which is conserved in all known ACC oxidases including the other previously reported banana ACC oxidase, Mh-ACO2. The locus consists of two nearly identical paralogous ACC oxidase genes arranged in opposite orientation and separated by a 3.1-kb intergenic region. The has only two introns, at positions identical to , which comprises a coding region interrupted by three introns. The predicted amino acid sequence of Mh-ACO1 shares less than 50% identity to those of ACC oxidase from other climacteric fruits, while that of Mh-ACO2 shows more than 65% homology. When expressed in Saccharomyces cerevisiae -encoded protein possessed the enzyme activity for ethylene conversion. The levels of mRNA corresponding to both and increased during fruit ripening and were induced by exogenous ethylene. We conclude that both and contribute to increased ethylene production in fruits and these two genes are differentially expressed in fruits and other organs in banana.  相似文献   

13.
Amylose content and amylopectin chain length distribution, the two most commonly used structural parameters of starch, have significant effects on starch retrogradation. In the present work, starches were separated and purified from 18 rice cultivars. The amylopectin was purified from each starch. Amylopectin chain length distribution was analyzed by high-performance size-exclusion chromatography after debranched using isoamylase. The blue value was used to measure the amylose content before and after the defatting of starch. The amount of amylose associated with lipid was calculated. Pulsed nuclear magnetic resonance was used to follow the retrogradation of starch both in cooked rice grains and in the purified form. The Avrami equation was employed to describe the retrogradation kinetics of rice starch. To look into the relationship between the starch structure and retrogradation behavior, the structural parameters were correlated with retrogradation kinetics parameters using both Pearson and partial correlations. The results indicated the following: first, the retrogradation behavior of rice starch remains similar in both the purified form and cooked rice grains; second, the peak value of amylopectin short-chain length has a significant positive relationship with the amylopectin crystallization rate constant k; third, the amylose content after defatting has a significant positive relationship with the parameter k and a negative relationship with the Avrami exponent n; and fourth, the amount of amylose associated with lipid has a negative relationship with the parameter k.  相似文献   

14.
The hypothesis of increasing the branch density of starch to reduce its digestion rate through partial shortening of amylopectin exterior chains and the length of amylose was investigated. Starch products prepared using beta-amylase, beta-amylase and transglucosidase, maltogenic alpha-amylase, and maltogenic alpha-amylase and transglucosidase showed significant reduction of rapidly digested starch by 14.5%, 29.0%, 19.8%, and 31.0% with a concomitant increase of slowly digested starch by 9.0%, 19.7%, 5.7%, and 11.0%, respectively. The resistant starch content increased from 5.1% to 13.5% in treated starches. The total contents of the prebiotics isomaltose, isomaltotriose, and panose (Isomaltooligosaccharides) were 2.3% and 5.5%, respectively, for beta-amylase/transglucosidase- and maltogenic alpha-amylase/transglucosidase-treated starches. The molecular weight distribution of enzyme-treated starches and their debranched chain length distributions, analyzed using high-performance size-exclusion chromatography with multiangle laser light scattering and refractive index detection (HPSEC-MALLS-RI) and HPSEC-RI, showed distinctly different patterns among starches with different enzyme treatments. A larger proportion of low molecular weight fractions appeared in starches treated additionally with transglucosidase. All enzyme-treated starches showed a mixture of B- and V-type X-ray diffraction patterns, and 1H NMR spectra showed a significant increase of alpha-1,6 linkages. Both the increase of the starch branch density and the crystalline structure in the treated starches likely contribute to their slow digestion property.  相似文献   

15.
Structural characteristics of native and annealed Peruvian carrot (Arracacia xanthorrhiza) starches were determined and compared to those of cassava and potato starches. Peruvian carrot starch presented round and irregular shaped granules, low amylose content and B-type X-ray pattern. Amylopectin of this starch contained a large proportion of long (DP > 37) and short (DP 6-12) branched chains. These last ones may contribute to its low gelatinization temperature. After annealing, the gelatinization temperatures of all starches increased, but the ΔH and the crystallinity increased only in Peruvian carrot and potato starches. The annealing process promoted a higher exposure of Peruvian carrot amylose molecules, which were more quickly attacked by enzymes, whereas amylopectin molecules became more resistant to hydrolysis. Peruvian carrot starch had structural characteristics that differed from those of cassava and potato starches. Annealing affected the semicrystalline structure of this starch, enhancing its crystallinity, mainly due to a better interaction between amylopectin chains.  相似文献   

16.
甘薯淀粉产量及相关性状的遗传多样性和关联度分析   总被引：1，自引：0，他引：1  
甘薯[Ipomoea batatas(L.)Lam.]是加工淀粉和燃料乙醇的重要原料,是目前我国最具开发前景的非粮食类新型能源作物。选育高淀粉产量的能源型甘薯新品种是甘薯育种的重要目标。为了获得准确筛选高淀粉产量育种材料的性状指标,提高甘薯高淀粉产量育种效率,缩短育种周期,本研究利用不同甘薯品种(系)的自然变异,根据淀粉产量、不同生长发育阶段的5个主要农艺性状和3个淀粉合成关键酶活性测定结果,利用相似系数和遗传距离矩阵,以类平均法对国内48份不同淀粉产量甘薯种质资源进行了遗传多样性分析,通过关联度分析研究了淀粉产量与不同时期农艺性状、淀粉合成关键酶活性的相关性。结果表明:48份甘薯种质资源材料在不同时期农艺特征差异较大;不同时期农艺性状的聚类结果中,栽后100 d的农艺性状与淀粉产量关联度最大,淀粉产量与该时期的基部分枝数呈极显著负相关(r=0.428),与干率呈极显著正相关(r=0.423),而与最长蔓长、单株结薯数和单株鲜薯重相关性不显著。48份甘薯种质材料在不同时期的酶活聚类结果差异明显。不同时期的甘薯淀粉合成关键酶活性聚类结果中,栽后50 d酶活聚类与淀粉产量聚类结果关联度最大,淀粉产量与该时期测得的ADPG焦磷酸化酶(ADPG-PPase)活性呈负相关关系(r=0.163),与蔗糖合成酶(SS)活性(r=0.101)、蔗糖磷酸合成酶(SPS)活性(r=0.016)呈正相关,但相关性均未达到显著水平。加之淀粉合成关键酶活性测定步骤繁琐,不适宜作为甘薯高淀粉产量育种早期选择的生理指标。在高淀粉产量育种材料筛选时可于栽后100 d对农艺性状进行综合考察,重点考虑干率较高及分枝数较少的品系。本研究可为甘薯高淀粉产量育种提供一定的理论依据。  相似文献   

17.
Chemical composition, molecular structure and organization, and thermal and pasting properties of maize and potato starches fractionated on the basis of granule size were investigated to understand heterogeneity within granule populations. For both starches, lipid, protein, and mineral contents decreased and apparent amylose contents increased with granule size. Fully branched (whole) and debranched molecular size distributions in maize starch fractions were invariant with granule size. Higher amylose contents and amylopectin hydrodynamic sizes were found for larger potato starch granules, although debranched molecular size distributions did not vary. Larger granules had higher degrees of crystallinity and greater amounts of double and single helical structures. Systematic differences in pasting and thermal properties were observed with granule size. Results suggest that branch length distributions in both amylose and amylopectin fractions are under tighter biosynthetic control in potato starch than either molecular size or amylose/amylopectin ratio, whereas all three parameters are controlled during the biosynthesis of maize starch.  相似文献   

18.
设施油桃果实发育过程中有机酸代谢的研究   总被引：6，自引：0，他引：6  
以设施栽培"超红珠"油桃为试材,测定了果实发育过程有机酸含量及相关代谢酶——柠檬酸合酶(CS)、苹果酸酶(ME)、苹果酸脱氢酶(MDH)的活性,并对果实中有机酸积累及酶活性的关系进行了分析。研究结果表明:随油桃果实发育,其有机酸含量呈先升高后降低趋势,于盛花后49d达到最高值;苹果酸含量与总有机酸含量变化趋势相似;柠檬酸含量呈逐渐升高趋势,至果实成熟有所降低;果实成熟期苹果酸与柠檬酸含量相近。有机酸相关代谢酶CS活性变化与柠檬酸含量相关性不大;果实发育后期ME活性逐渐升高,促进了苹果酸的降解和转化;MDH活性变化与苹果酸含量显著相关。因此抑制果实发育前期MDH的活性、促进果实发育后期ME的活性可以降低果实酸含量,提高糖酸比。  相似文献   

19.
This study was conducted to investigate the inhibitory effects of palatinose and Palatinit, which are disaccharides (or disaccharide alcohol) connected through an alpha-1,6-glucosyl linkage, on the hydrolysis of other carbohydrates, using an enzyme extract from the rat small intestine and a purified sucrase-isomaltase complex. Palatinose and its hydrogenated product, Palatinit, an equimolar mixture of alpha-O-D-glucopyranosyl-1,6-D-sorbitol (GPS) and alpha-O-D-glucopyranosyl-1,6-D-mannitol (GPM), inhibited the hydrolysis of sucrose and maltose. Palatinose and Palatinit also inhibited the hydrolysis of dextrin and soluble starch. Kinetic analysis of the enzymatic inhibition by GPS and GPM on sucrose hydrolysis revealed that both GPS and GPM competitively inhibit sucrase catalytic activity. These results suggest that disaccharides with an alpha-1,6-glucosyl linkage competitively inhibit intestinal alpha-glucosidases and may reduce the rate of hydrolysis of sucrose and other alpha-glucosylsaccharides.  相似文献   

20.
为探究不同类型玉米淀粉形成机理,对普通玉米、甜玉米、糯玉米淀粉积累、相关酶活及基因表达进行测定,分析不同类型玉米淀粉积累、相关酶活及基因表达之间的差异及相互关系。结果表明,不同类型玉米总淀粉和直链淀粉百分含量为:普通玉米>糯玉米>甜玉米,支链淀粉百分含量为:糯玉米>普通玉米>甜玉米,灌浆期间总淀粉和直链淀粉含量3个玉米类型间差异显著;灌浆期间,普通玉米各淀粉合成相关酶活性最高,甜玉米淀粉合成相关酶活性最低,糯玉米则介于普通玉米和甜玉米之间,但其GBSS酶活性很小。灌浆期间3个类型玉米除GBSS酶活性差异不显著外,其他淀粉合成相关酶活性差异显著;普通玉米淀粉合成相关基因表达量总体均高于甜玉米和糯玉米,甜玉米和糯玉米相关突变基因仍存在表达。表明不同类型玉米淀粉含量和组成上差异明显;普通玉米淀粉的形成需要淀粉合成相关酶相互作用,淀粉合成相关酶活性的缺失会改变淀粉组成;不同类型玉米淀粉合成相关基因表达差异显著,但都存在转录活性。对普通玉米进行相关性分析同时发现,淀粉的合成不仅受到转录调控,还受到转录后调控,淀粉的合成是淀粉合成各酶之间相互协调的结果。  相似文献   

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