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At least 19 recordsLinked to original sources
PubMed1975

Isolation of amylopectin granules and identification of amylopectin phosphorylase in the oocysts of Eimeria tenella.

Amylopectin granules were purified from Eimeria tenella oocysts following digestion with sodium dodecyl sulfate and pronase. The oval granules had a uniform size of 0.5 X 0.7 mum, and consisted of only glucose polymers. alpha-Amylase treatment yielded 235 nmoles of maltose from the granules from 10(6) unsporulated oocysts and 93 nmoles maltose from those from 10(6) sporulated oocysts. Amylopectin phosphorylase activity was detected in the cytoplasm of unsporulated oocysts of E. tenella. It had a specific activity of 13 U/mg protein in crude extracts, and a pH optimum of 6.0. The Km values determined were 9.1 mM for glucose-1-phosphate and 5.6 mM for glucose end groups in potato amylopectin. Enzyme activity declined at a linear rate during sporulation, sporulated oocysts containing less than 8% of the activity of unsporulated oocysts. No amylase-type activity was found in the parasite.

Amylopectin↗
PubMed1996

Amylopectin starch induces nonreversible insulin resistance in rats.

Starches that are high in amylopectin are digested and absorbed more quickly than starches with a high amylose content and produce insulin resistance in rats during long-term feeding. The aim of this study was to determine whether amylopectin-induced insulin resistance could be prevented or reversed by a period of high amylose feeding. We employed a randomized design in which two groups of rats were fed either the high amylose and then the high amylopectin diet for two consecutive 8-wk periods or vice versa (high amylopectin and then high amylose). Four other groups were fed either a high amylose or a high amylopectin diet for 8 or 16 wk. All rats were fed two 10-g meals per day (300 kJ/d), and insulin sensitivity was assessed by intravenous glucose tolerance test (IVGTT) after 8 or 16 wk of feeding. We found no difference in glucose tolerance between any group at any time point. Insulin responses, however, were 50% higher (P < 0.01) after 16 wk of high amylopectin feeding [area under the plasma insulin curve (AUC) = 18.1 +/- 1.4 nmol.L-1 x 15 min] compared with high amylose feeding (AUC = 13.0 +/- 1.2 nmol.L-1 x 15 min). The two groups which received both diets developed a similar degree of insulin resistance, equivalent to that after 16 wk of high amylopectin feeding. The findings suggest that amylopectin-induced insulin resistance cannot be reversed or prevented by either a subsequent or previous period of amylose feeding. Taken together, the data suggest that the nature of starch in the Western diet influences the development of noninsulin-dependent diabetes mellitus in humans.

Amylopectin↗
PubMed1996

The chemical structure of amylose and amylopectin fractions of starch from tobacco leaves during development and diurnally-nocturnally.

Starches, isolated from rapidly expanding tobacco leaves four times during the day and night and once from fully expanded leaves, were fractionated with concanavalin A. From an examination of the amounts and properties of amylose, the diurnal decrease in iodine absorption of the starches on illumination appeared to be due to an increase in its branched character, and possibly the presence of unbranched polymer of low dp, combined with a decrease in the proportion of amylose fraction. The increase in apparent amylose content with age was due to an increase in the proportion of amylose. The amylose fractions at different times had only small differences in average mol size in solution and relative mol wt (M(r) near 4 x 10(5)) which were lower than those of storage organs. The average mol size in solution and relative mol wt of the amylopectins decreased during illumination, increased in darkness, and were lower (M(r) 2-2.7 x 10(6)) at all times than those from storage organs. Debranching followed by size-exclusion chromatography [on Fractogel TSK 50(S)] gave similar proportions of long, medium, and short chains for all amylopectin samples, and these proportions differed from those for debranched amylopectin from n-maize seed starch. On debranching and chromatography of the amylopectin beta-limit dextrins (which gives an estimate of the proportions of core chains) differences persisted. Structural characteristics of amylopectin from tobacco leaf starch were similar to those of normal genotypes from storage organs. The proportion of glucosyl units in core chains, the external-to-core chain ratio, and indices of compactness were calculated for a number of (1-->4)(1-->6) alpha-glucans. A plot of the index of compactness for glycogens and amylopectins showed that the decrease in compactness and the increase in total average chain length that occurs from glycogen to normal and then to amylose extender amylopectins involves a proportionate increase in average internal, external, and core chain lengths and not a selective increase in one type of chain.

Amylopectin↗
PubMed1991

Starch flavor: apparent discrimination between amylopectin and amylose by rats.

Rats given a choice between dilute suspensions of corn amylopectin and corn amylose generally preferred amylopectin. The preference threshold for amylopectin was lower than the preference threshold for amylose (0.1% and 0.5%, respectively). Two sources of evidence indicate that the difference in preference for these two types of starch is due to an off-taste component in corn amylose rather than to an ability to discriminate between amylopectin and amylose per se: 1) rats given a choice of purified amylopectin and amylose from potato did not show a significant preference, and 2) aqueous extracts of amylose reduce preference for water and amylopectin, respectively. Extensive washing of corn amylose with ammonia-methanol, water and methanol did not completely remove the off-taste of corn amylose. Despite the difference in off-taste, rats trained to avoid amylopectin also avoided amylose. It is proposed that starch has two flavor components: a component due to starch itself that induces preference, and a component due to impurities that reduces preference.

Amylopectin↗
PubMed1998

Growth factor release from amylopectin hydrogel based on copper coordination.

This paper describes a biodegradable hydrogel matrix releasing basic fibroblast growth factor (bFGF) on the basis of protein metal coordination with the protein drug. The biodegradable hydrogel was prepared from amylopectin by its crosslinking with ethylene glycol diglycidyl ether, followed by introduction of diethylenetriaminepentaacetic acid (DTPA) residues for copper chelation. When bFGF was incorporated into the DTPA-introduced amylopectin hydrogel after chelation with Cu2+, an insignificant amount of bFGF was released from the hydrogel in buffered solution, in contrast to that without Cu2+ chelation. An increased ionic strength in the solution did not affect the bFGF release, indicating the occurrence of coordinate bonding of bFGF to the DTPA-introduced hydrogel through Cu2+ chelation. An implantation study with 125I-labeled amylopectin hydrogels demonstrated that they underwent degradation in the back subcutis of mice. Cu2+ chelation of hydrogels enabled bFGF to remain in the mouse back for a long time period, irrespective of DTPA introduction. However, DTPA residues were necessary to induce significant neovascularization by the Cu2+-chelating hydrogels incorporating bFGF. The DTPA-introduced amylopectin prevented Cu2+-induced deactivation of bFGF, again in marked contrast to DTPA-free amylopectin. It was concluded that biologically active bFGF could be incorporated to DTPA-introduced amylopectin through Cu2+ chelation in a stabilized state and was released as a result of hydrogel biodegradation, resulting in prolonged neovascularization.

Amylopectin↗
PubMed1975

Studies on the binding of amylopectin sulfate with gastric mucin.

Amylopectin sulfate, a sulfated polysaccharide that has an antipeptic property, was examined for its ability to bind gastric mucins. After chemically cross-linking the amylopectin sulfate into an insoluble gel, its binding with mucins isolated from antral and fundic mucosa of canine stomachs was studied with chromatography. A component present in both mucin fractions bound to the amylopectin sulfate gel below pH 4.5. This binding was reversible, and the complex dissociated above pH 5. Similar binding properties were found with soluble amylopectin sulfate. The component of the mucine which bound to amylopectin sulfate differed from the one which did not bind in its electrophoretic mobility and in its higher proportion of basic amino acids and a lower hexosamine, serine, and threonine content. This study suggests that amylopectin sulfate may bind to gastric mucins only under conditions of low pH.

Amino Acids↗
PubMed1994

Inhibition of amylopectin retrogradation by partial beta-amylolysis.

The rate of retrogradation of amylopectin solution differs from one starch variety to another and it is thought to be due to the different length of the external chains of amylopectin. A shortening of the external chains of waxy maize and potato amylopectin was performed with beta-amylase. Partial beta-amylolysis produced a significant fraction of chains having 2-6 glucose units. A high linear correlation (R > 0.97) was found between the enthalpy of retrograded amylopectin measured by DSC, or percent solid measured by low frequency pulsed NMR, and average external chain length. No retrogradation appeared to occur when the external chains of both amylopectins had 11 or less glucose units on average. The inhibition of retrogradation appears to be caused primarily by the presence of very short external chains, which hinders the reassociation of the long external chains.

Amylopectin↗
PubMed1985

Induction of colorectal adenocarcinoma in rats by amylopectin sulfate.

The carcinogenicity of orally administered amylopectin sulfate was studied in F344 rats. Amylopectin sulfate induced adenomas and adenocarcinomas in the rat colorectum. The incidences of tumor induction in groups that were given a 5% diet of amylopectin sulfate for 3, 6 and 9 months were 2 out of 20 rats (10%), 9 out of 20 rats (45%) and 12 out of 20 rats (60%), respectively. Squamous metaplasia of the colorectum persisted in all rats and progressed irreversibly. Amylopectin sulfate was deposited in the colorectal lamina propria, submucosa and regional lymph nodes. Amylopectin sulfate induced a lesion similar to that produced by degraded carrageenan in the rat colorectum.

Adenocarcinoma↗
PubMed1985

Rapid analysis of starch, amylose and amylopectin by high-performance size-exclusion chromatography.

Starch components, amylose and amylopectin, were analyzed by high-performance size-exclusion chromatography. These two-components were separated using a two-column system (E-Linear and E-1000) and dimethyl sulphoxide as the mobile phase. The void volume (V0 = 2.22 ml) was measured using tobacco mosaic virus. Column calibration was accomplished with dextrans of known average molecular weight (Mw range = 10,100-2,000,000). The elution volume of amylopectin (Ve = 2.5 ml) indicated that this starch component was fractionated on the column system despite its very large molecular size. Standard curves were prepared from various mixtures of purified corn and wheat amylose and amylopectin. From the linear relationships obtained, the percentages of both components in corn and wheat starches were determined. The method developed proved useful to monitor the purity of amylose and amylopectin preparations, and to estimate rapidly the amylose:amylopectin ratio of starch samples.

Amylopectin↗
PubMed1998

Amylose is synthesized in vitro by extension of and cleavage from amylopectin.

Amylose synthesis was obtained in vitro from purified Chlamydomonas reinhardtii starch granules. Labeling experiments clearly indicate that initially the major granule-bound starch synthase extends glucans available on amylopectin. Amylose synthesis occurs thereafter at rates approaching or exceeding those of net polysaccharide synthesis. Although these results suggested that amylose originates from cleavage of a pre-existing external amylopectin chain, such transfer of chains from amylopectin to amylose was directly evidenced from pulse-chase experiments. The structure of the in vitro synthesized amylose could not be distinguished from in vivo synthesized amylose by a variety of methods. Moreover high molecular mass branched amylose synthesis preceded that of the low molecular mass, suggesting that chain termination occurs consequently to glucan cleavage. Short pulses of synthesis followed by incubation in buffer with or without ADP-Glc prove that transfer requires the presence of the glucosyl-nucleotide. Taken together, these observations make a compelling case for amylopectin acting as the in vivo primer for amylose synthesis. They further prove that extension is followed by cleavage. A model is presented that can explain the major features of amylose synthesis in plants. The consequences of intensive amylose synthesis on the crystal organization of amylopectin are reported through wide angle x-ray analysis of the in vitro synthesized polysaccharides.

Amylopectin↗
PubMed1995

Amylopectin starch promotes the development of insulin resistance in rats.

Starches that are high in amylopectin are digested and absorbed more quickly than starches with a high amylose content and produce larger postprandial glucose and insulin responses. The aim of this study was to test the hypothesis that feeding rats a diet containing quickly digested starch could promote insulin resistance. Sprague-Dawley rats were fed either a high amylopectin or high amylose diet (two 10-g meals per day), and insulin sensitivity was assessed after 9 wk by intravenous glucose tolerance test (IVGTT). In the rats fed the high amylopectin diet, glucose tolerance was significantly lower (P < 0.05) and the insulin response to IVGTT was twice as high as in rats fed the high amylose diet (P < 0.05). A second study using Wistar rats investigated the time course of these changes. Differences in the insulin response to the IVGTT were not evident at 4 wk but began to emerge at 8 wk, and by 12 wk the insulin response was 100% greater in rats fed the high amylopectin diet (P < 0.05) than in those fed the high amylose diet. In addition, basal plasma insulin concentration was higher in rats fed the high amylopectin diet (P < 0.05). There were no differences, however, in glucose tolerance at any time point. The results suggests that quickly digested starch promotes the development of insulin resistance in rats. The relatively slow time course resembles the normal development of insulin resistance in humans.

Amylopectin↗
PubMed1998

Mutations in the gene encoding starch synthase II profoundly alter amylopectin structure in pea embryos.

Mutations at the rug5 (rugosus5) locus have been used to elucidate the role of the major soluble isoform of starch synthase II (SSII) in amylopectin synthesis in the developing pea embryo. The SSII gene maps to the rug5 locus, and the gene in one of three rug5 mutant lines has been shown to carry a base pair substitution that introduces a stop codon into the open reading frame. All three mutant alleles cause a dramatic reduction or loss of the SSII protein. The mutations have pleiotropic effects on the activities of other isoforms of starch synthase but apparently not on those of other enzymes of starch synthesis. These mutations result in abnormal starch granule morphology and amylopectin structure. Amylopectin contains fewer chains of intermediate length (B2 and B3 chains) and more very short and very long chains than does amylopectin from wild-type embryos. The results suggest that SSII may play a specific role in the synthesis of B2 and B3 chains of amylopectin. The extent to which these findings can be extrapolated to other species is discussed.

Amylopectin↗
PubMed1999

Simultaneous antisense inhibition of two starch-synthase isoforms in potato tubers leads to accumulation of grossly modified amylopectin.

A chimaeric antisense construct was used to reduce the activities of the two major starch-synthase isoforms in potato tubers simultaneously. A range of reductions in total starch-synthase activities were found in the resulting transgenic plants, up to a maximum of 90% inhibition. The reduction in starch-synthase activity had a profound effect on the starch granules, which became extremely distorted in appearance compared with the control lines. Analysis of the starch indicated that the amounts produced in the tubers, and the amylose content of the starch, were not affected by the reduction in activity. In order to understand why the starch granules were distorted, amylopectin was isolated and the constituent chain lengths analysed. This indicated that the amylopectin was very different to that of the control. It contained more chains of fewer than 15 glucose units in length, and fewer of between 15 and 80 glucose units. In addition, the amylopectin contained more very long chains. Amylopectin from plants repressed in just one of the activities of the two starch-synthase isoforms, which we have reported upon previously, were also analysed. Using a technique different to that used previously we show that both isoforms also affect the amylopectin, but in a way that is different to when both isoforms are repressed together.

Amylopectin↗
PubMed1994

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

Plant starch synthesis can be distinguished from those of bacterial, fungal, and animal glycogen by the presence of multiple elongation (starch synthases) and branching enzymes. This complexity has precluded genetic assignment of functions to the various soluble starch synthases in the building of amylopectin. In Chlamydomonas, we have recently shown that defects in the major soluble starch synthase lead to a specific decrease in the amount of a subset of amylopectin chains whose length ranges between 8 and 40 glucose residues (Fontaine, T., D'Hulst, C., Maddelein, M.-L., Routier, F., Marianne-Pepin, T., Decq, A., Wieruszeski, J. M., Delrue, B., Van Den Koornhuyse, N., Bossu, J.-P., Fournet, B., and Ball, S. G. (1993) J. Biol. Chem. 268, 16223-16230). We now demonstrate that granule-bound starch synthase, the enzyme that was thought to be solely responsible for amylose synthesis, is involved in amylopectin synthesis. Disruption of the Chlamydomonas granule-bound starch synthase structural gene establishes that synthesis of long chains by this enzyme can become an absolute requirement for amylopectin synthesis in particular mutant backgrounds. In the sole presence of soluble starch synthase I, Chlamydomonas directs the synthesis of a major water-soluble polysaccharide fraction and minute amounts of a new type of highly branched granular material, whose structure is intermediate between those of glycogen and amylopectin. These results lead us to propose that the nature of the elongation enzyme conditions the synthesis of distinct size classes of glucans in all starch fractions.

Amylopectin↗
PubMed1980

[Kinetic studies of the (1 linked to 4)-alpha-D-glucopyranosyltransferase reaction catalyzed by cyclodextrin glycosyltransferase, particularly the cyclization with amylose, amylopectin and total starch as substrate].

The time course of the (1 leads to 4)-alpha-D-glucopyranosyltransfer reactions catalyzed by the cyclodextrin glycosyltransferase ((1 leads to 4)-alpha-D-glucan: [(1 leads to 4)-alpha-D-glucopyranosyl]transferase (cyclizing), EC 2.4.1.19, CGT) from Klebsiella pneumoniae was studied with several commercial amyloses, potato starch, and amylopectin, respectively. Amyloses were poor substrates for the cyclization reaction. In the initial phase of the transfer reactions, the CGT catalyzed a rapid shortening of the amylose chains. The rate of this shortening reaction was significantly accelerated by addition of maltooligosaccharides. Maximum rate of cyclohexaamylose formation was reached with amylose chains sufficiently short (less than Glc100) for the cyclization reaction. Cyclohexaamylose was formed with maximum rate from amyloses containing amylopectin impurities in the initial phase of the transfer reactions, suggesting that the non-reducing ends of the outer amylopectin chains serve as acceptors for the disproportionation of the amylose. Accordingly, water-soluble, high-molecular-weight products containing higher percentages of lengthened outer-chains were obtained from potato starch or amylopectin. In the course of the transfer reactions, only traces of smaller maltooligosaccharides were detected chromatographically.

Amylopectin↗
PubMedDate not supplied

Amylopectin synthase of Eimeria tenella: identification and kinetic characterization.

A soluble enzyme amylopectin synthase (UDP-glucose-alpha 1,4-glucan alpha-4-glucosyltransferase) which transfers glucose from uridine 5'-diphosphate glucose (UDP-glucose) to a primer to form alpha-1,4-glucosyl linkages has been identified in the extracts of unsporulated oocysts of Eimeria tenella. UDP-glucose and not ADP-glucose was the most active glucosyl donor. Corn amylopectin, rabbit liver glycogen, oyster glycogen and corn starch served as primers; the latter two were less efficient. The enzyme has an apparent pH optimum of 7.5 and exhibited typical Michaelis-Menten kinetics with dependence on both the primer and substrate concentrations. The Michaelis constants (Km), with respect to UDP-glucose, was 0.5 mM; and 0.25 mg/ml and 1.25 mg/ml with respect to amylopectin and rabbit liver glycogen. The product formed by the reaction was predominantly a glucan containing alpha-1,4 linkages. The specificity of the enzyme suggests that this enzyme is similar to glycogen synthase in eukaryotes and has been designated as amylopectin synthase (UDP-glucose-alpha-1,4-glucosetransferase EC 2.4.1.11).

Amylopectin↗
PubMed1973

Amylopectin sulphate (SN-263) coats the gastric mucosal surface.

After the application in vitro of (14)C amylopectin sulphate solution to frozen sections of human ulcer-bearing stomach, autoradiography demonstrates localization of amylopectin sulphate to the gastric surface. The affinity of amylopectin sulphate macromolecule for the gastric luminal surface would provide a substrate-bound pepsin inhibitor with a molecular sieve-like action to exclude proteolytic enzymes from the mucosal surface. This protective coating action may mimic the hypothetical role of endogenous gastric mucous substances and account for the action of amylopectin sulphate in human peptic ulcer.

Amylopectin↗
PubMed1995

Failure of liver transplantation to diminish cardiac deposits of amylopectin and leukocyte inclusions in type IV glycogen storage disease.

Orthotopic liver transplantation has been used to treat glycogen storage disease type IV. Most long-term surviving patients who have undergone liver transplantation have been free of neuromuscular and cardiac morbidity, and regression of cardiac amylopectin infiltration has been reported after liver transplantation. Leukocyte inclusions in glycogen storage disease type IV have also been reported. We present the case of a child who underwent orthotopic liver transplantation for glycogen storage disease type IV. In contrast to previous reports, at autopsy 2 1/2 years after transplantation, there was massive amylopectin deposits in his heart. Further, peripheral leukocytes never showed loss of amylopectin inclusions after transplantation. Orthotopic liver transplantation for type IV glycogen storage disease may not, in all cases, result in improvement in other affected organs. Consideration of multiorgan transplantation appears warranted.

Amylopectin↗