Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Amylose”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed2002

The altered pattern of amylose accumulation in the endosperm of low-amylose barley cultivars is attributable to a single mutant allele of granule-bound starch synthase I with a deletion in the 5'-non-coding region.

Reasons for the variable amylose content of endosperm starch from waxy cultivars of barley (Hordeum vulgare) were investigated. The mature grains of most such cultivars contain some amylose, although amounts are much lower than in wild-type cultivars. In these low-amylose cultivars, amylose synthesis starts relatively late in grain development. Starch granules in the outer cell layers of the endosperm contain more amylose than those in the center. This distribution corresponds to that of granule-bound starch synthase I (GBSSI), which is more severely reduced in amount in the center of the endosperm than in the outer cell layers, relative to wild-type cultivars. A second GBSSI in the barley plant, GBSSIb, is not detectable in the endosperm and cannot account for amylose synthesis in the low-amylose cultivars. The change in the expression of GBSSI in the endosperm of the low-amylose cultivars appears to be due to a 413-bp deletion of part of the promoter and 5'-untranslated region of the gene. Although these cultivars are of diverse geographical origin, all carry this same deletion, suggesting that the low-amylose cultivars have a common waxy ancestor. Records suggest a probable source in China, first recorded in the 16th century. Two further families of waxy cultivars have no detectable amylose in the endosperm starch. These amylose-free cultivars were selected in the 20th century from chemically mutagenized populations of wild-type barley. In both cases, 1-bp alterations in the GBSSI gene completely eliminate GBSSI activity.

5' Flanking Region↗
PubMed1997

Fecal numbers of bifidobacteria are higher in pigs fed Bifidobacterium longum with a high amylose cornstarch than with a low amylose cornstarch.

Twelve young male pigs consumed a purified diet containing wheat bran as fiber source. Starch provided 50% of total daily energy either as a low amylose cornstarch or as a high amylose (amylomaize) starch. The pigs were given a supplement of a freeze-dried probiotic organism (Bifidobacterium longum CSCC 1941). A block crossover design was used so that at any one time two groups of three pigs consumed either the high or low amylose cornstarch without probiotic and a further two groups of three pigs consumed either high or low amylose cornstarch with probiotic. Neither food intake nor body weight gain was affected by diet. Fecal output was higher when pigs were fed the high amylose cornstarch, but moisture content was unaffected. Fecal concentrations and excretion of total volatile fatty acids were higher when pigs were fed the high amylose cornstarch. Concentrations of acetate were unaffected by dietary starch, but those of propionate and butyrate were higher when the high amylose cornstarch was consumed. Fecal excretion of all three acids was higher during high amylose cornstarch feeding. Bifidobacteria were detected in the feces only when pigs were fed Bifidobacterium longum. Fecal bifidobacteria counts (expressed per gram of wet feces) and their daily fecal excretion were higher when pigs were fed high amylose cornstarch. Feeding the probiotic did not alter fecal starch or volatile fatty acids. None of the variables studied was affected by the order of feeding of starch or probiotic. The data show that a high amylose starch acts as a prebiotic in promoting the fecal excretion of probiotic organisms.

Amylose↗
PubMedDate not supplied

Amphiphilic block copolymer with a molecular recognition site: induction of a novel binding characteristic of amylose by self-assembly of poly(ethylene oxide)-block-amylose in chloroform.

Solution properties of amphiphilic methoxy poly(ethylene oxide)-block-amyloses (MPEO-amyloses) in chloroform were investigated by SLS and DLS. The results indicated that MPEO-amyloses dissolved in chloroform containing 2 wt % DMSO by their self-associations. The complexation of MPEO-amylose with methyl orange (MO) was significantly enhanced in the amylose domain of the associate in chloroform. The blue shift of the maximum absorption and strong induced circular dichroism with exciton coupling were observed in the MPEO-amylose MO complex in chloroform. The self-assembly of MPEO-amylose in chloroform shows a unique feature for binding with MO. MPEO-block-amylose is a novel amphiphilic polymer with amylose as a molecular recognition site.

Amylose↗
PubMed1976

Beta-amylase-resistant amylose. Effect of urea on the limited hydrolysis of amylose by beta-amylase.

Amylose prepared from starch dispersed in 10M-urea, pH6.2, was found to be resistant to the action of beta-amylase and phosphorylase, though it was degraded by alpha-amylase. Amylose isolated by conventional methods was similarly refractory after urea treatment, and was hydrolysed by beta-amylase to the extent of 32-35%; it had no inhibitory effect towards beta-amylase. The physical and chemical properties of the modified amylose were in general comparable with those of normal amylose with a beta-amylolysis limit of 94-98%. Starch and amylopectin were unaffected by urea treatment, i.e. the presence of amylopectin protected amylose against changes induced in it by urea. It is speculated that urea treatment "freezes" amylose molecules in a conformation that renders non-reducing termini inaccessible to the active site of the exo-enzymes. Such changes may limit the degradative action of beta-amylase and phosphorylase.

Amylases↗
PubMed1984

Structure studies of amylose-V complexes and retrograded amylose by action of alpha amylases, and a new method for preparing amylodextrins.

Human-salivary, porcine-pancreatic, and Bacillus subtilis alpha amylases were used to study the structure of amylose-V complexes with butyl alcohol, tert-butyl alcohol, 1,1,2,2-tetrachloroethane, and 1-naphthol, and of retrograded amylose. Alpha amylase hydrolyzes the amorphous, folding areas on the surfaces of the lamella of packed helices, with the formation of resistant, amylodextrin fragments. Their degree of polymerization (d.p.) corresponds to the diameter of the helices and the folding length of the chain. The resistant fragments were fractionated on a column of Bio-Gel A-0.5m. Gel filtration of human-salivary and porcine-pancreatic alpha amylase hydrolyzates gave resistant fragments whose peak fractions, i.e., the three pooled fractions from the gel-filtration column with the highest amount of carbohydrate, had a d.p. of 75 +/- 4 for the amylose complex with butyl alcohol, 90 +/- 3 for those with tert-butyl alcohol and tetrachloroethane, and 123 +/- 2 for that with 1-naphthol. These d.p. values correspond to helices of six residues per turn with a folding length of 10 nm, seven residues per turn with a folding length of 10 nm, and eight residues per turn with a folding length of 12 nm (or nine residues per turn with a folding length of 10 nm), respectively. Acid hydrolysis of retrograded amylose gave a resistant fragment having an average d.p. of 32, human-salivary and porcine-pancreatic alpha amylases gave a resistant fragment of d.p. 43, and Bacillus subtilis alpha amylase gave a resistant fragment of d.p. 50. A structure for retrograded amylose is proposed in which there are crystalline, double-helical regions that are 10 nm long, interspersed with amorphous regions. The amorphous regions are hydrolyzed by acid and by alpha amylases, leaving the crystalline regions intact. The differences in the sizes of the resistant amylodextrins depend on the differences in the specificities of the hydrolyzing agents: acid hydrolyzes right up to the edge of the crystalline region, whereas the alpha amylases hydrolyze up to some point several D-glucosyl residues away from the crystalline region, leaving "stubs" on the ends of the amylodextrins whose sizes are dependent on the sizes of the binding sites of the individual alpha amylases.(ABSTRACT TRUNCATED AT 400 WORDS)

Alcohols↗
PubMed2003

Synthesis of amylose acetates and amylose sulfates with high structural uniformity.

Amylose triacetate (ATA) dissolved in DMSO was partially deacetylated by 1,6-hexamethylendiamine, 1,8-octamethylendiamine, 1,12-dodecylmethylendiamine and 1,2-cyclohexyldiamine (mixture of cis and trans isomers) at 80 degrees C. The reaction kinetics of the deacetylation were studied. Differences were found in the course of the reaction depending on the type of alkylene diamine (linear or cyclic). The isolated amylose acetates were dissolved in DMF and subsequently sulfated with sulfamic acid. In the course of the sulfation, the acetyl groups acted as protective groups and were completely cleaved after reaction. The amylose acetates and sulfates obtained were studied by 13C NMR spectroscopy and elemental analysis. It could be shown, that the deacetylation of ATA with the described alkylene diamines as well as the subsequent sulfation are highly regioselective. By proceeding this reaction scheme it is possible to synthesize 6-amyloseacetate, 2,6-di-amyloseacetate and 2-amylosesulfate with a high structural uniformity.

Acetates↗
PubMed2005

Ultrastructure of individual and compound starch granules in isolation preparation from a high-quality, low-amylose rice, ilpumbyeo, and its mutant, G2, a high-dietary fiber, high-amylose rice.

The ultrastructures of isolated starch granules from Ilpumbyeo (IP), a low-amylose japonica rice, and its mutant, Goami2 (G2), a high-amylose rice, which have extreme contrasts in physicochemical properties, cooking qualities (Kang, H. J.; Hwang, I. K.; Kim, K. S.; Choi, H. C. Comparative structure and physicochemical properties of Ilpumbyeo, a high-quality japonica rice, and its mutant, Suweon 464. J. Agric. Food Chem. 2003, 51, 6598-6603. Kim, K. S.; Kang, H. J.; Hwang, I. K.; Hwang, H. G.; Kim, T. Y.; Choi, H. C. Comparative ultrastructure of Ilpumbyeo, a high-quality japonica rice, and its mutant, Suweon 464: Scanning and transmission electron microscopy studies. J. Agric. Food Chem. 2004, 52, 3876-3883), and susceptibility to amylolytic enzymes (Kim, K. S.; Kang, H. J.; Hwang, I. K.; Hwang, H. G.; Kim, T. Y.; Choi, H. C. Fibrillar microfilaments associated with a high-amylose rice, Goami2, a mutant of Ilpumbyeo, a high-quality japonica rice. J. Agric. Food Chem. 2005, 53, 2600-2608), were compared. In isolated preparation, IP consisted entirely of well-separated individual starch granules (ISG), whereas G2 consisted of two populations, the large voluminous bodies and the smaller forms, the ISGs. High-voltage electron microscopy revealed that each of the voluminous bodies consisted of tightly packed smaller subunits, the ISGs, indicating that they represent the compound starch granules (CSGs) of G2. This suggests that the structural as well as functional unit of G2 involved in food processing is, unlike IP and other ordinary rices, not ISG but is primarily CSG. ISGs located at the periphery of CSGs were fused to each other with adjacent ones forming a thick band or wall encircling the entire circumference. The periphery of ISGs separated from CSGs of G2 consisted of thin radially oriented filaments arranged side by side along the entire granule surface, whereas no such filaments occurred in ISG of IP. It appears that the thick band and the peripheral filaments surrounding CSGs and ISGs, respectively, function as a structural barrier that limits the entrance of water into the granules and subsequent absorption, causing the low swelling power, incomplete gelatinization, and finally poor quality of cooked rice in G2.

Amylose↗
PubMed2002

Vine-twining polymerization: amylose twines around polyethers to form amylose-polyether inclusion complexes.

In this paper, we describe a new polymerization manner termed as "vine-twining polymerization" to produce amylose-polymer inclusion complexes. The polymerization was achieved by an enzymatic polymerization of alpha-D-glucose-1-phosphate monomer catalyzed by phosphorylase in the presence of polyTHF as a guest polymer. The structure of the product was determined by X-ray powder diffraction and (1)H NMR measurements to be the inclusion complex. The formation process of the inclusion complexes during the polymerization was also evaluated. Furthermore, the formation of the inclusion complexes by this polymerization method by using polyTHFs with various M(n)s and end groups, as well as other polyethers as the guest polymers, was examined.

Amylose↗
PubMedDate not supplied

Crystallinity and morphology in films of starch, amylose and amylopectin blends.

Films of potato starch, amylose, and amylopectin and blends thereof were prepared by solution casting and examined using X-ray diffraction, light microscopy, transmission electron microscopy, and differential scanning calorimetry. Amylose films had a relative crystallinity of about 30% whereas amylopectin films were entirely amorphous. Blending of amylose and amylopectin resulted in films with a considerably higher degree of crystallinity than could be predicted. This is explained by cocrystallization between amylose and amylopectin and possibly by crystallization of amylopectin. The crystallized material gave rise to an endotherm detected with differential scanning calorimetry. The enthalpy and peak temperature of the transition also increased as the water content decreased. When the amylose proportion in the blends was low, separate phases of amylose and amylopectin were observed by light microscopy. At higher amylose proportions, however, the phase separation was apparently prevented by amylose gelation and the formation of a continuous amylose network. The amylose network in the films, observed with transmission electron microscopy, consisted of stiff strands and open pores and became less visible as the amylose proportion decreased. The water content of the films was dependent on the microstructure and the crystallinity.

Amylopectin↗
PubMed1997

A high amylose (amylomaize) starch raises proximal large bowel starch and increases colon length in pigs.

Young male pigs consumed a diet of fatty minced beef, safflower oil, skim milk powder, sucrose, cornstarch and wheat bran. Starch provided 50% of total daily energy either as low amylose cornstarch, high amylose (amylomaize) cornstarch or as a 50/50 mixture of corn and high amylose starch. Neither feed intake nor body weight gain as affected by dietary starch. Final plasma cholesterol concentrations were significantly higher than initial values in pigs fed the 50/50 mixture of corn and high amylose starch. Biliary concentrations of lithocholate and deoxycholate were lower in pigs fed high amylose starch. Large bowel length correlated positively with the dietary content of high amylose starch. Concentrations of butyrate in portal venous plasma were significantly lower in pigs fed high amylose starch than in those fed cornstarch. Neither large bowel digesta mass nor the concentrations of total or individual volatile fatty acids were affected by diet. However, the pool of propionate in the proximal colon and the concentration of propionate in feces were higher in pigs fed amylose starch. Concentrations of starch were uniformly low along the large bowel and were unaffected by starch type. In pigs with cecal cannula, digesta starch concentrations were higher with high amylose starch than with cornstarch. Electron micrographic examination of high amylose starch granules from these animals showed etching patterns similar to those of granules obtained from human ileostomy effluent. It appears that high amylose starch contributes to large bowel bacterial fermentation in the pig but that its utilization may be relatively rapid.

Amylose↗
PubMed2001

Both binding sites of the starch-binding domain of Aspergillus niger glucoamylase are essential for inducing a conformational change in amylose.

The interaction of the two binding sites of the starch-binding domain (SBD) of Aspergillus niger glucoamylase 1 (GA-I) with substrate has been investigated by using atomic force microscopy (AFM) and UV difference spectroscopy in combination with site-specific mutants of both SBD and GA-I. The SBD possesses two binding sites with distinct affinities towards the soluble linear substrate maltoheptaose; dissociation constants (K(d)) of 17 and 0.95 microM were obtained for W563 K (binding site 2 mutant) and W590 K (binding site 1 mutant), respectively, compared to an apparent K(d) of 23 microM for the wild-type SBD. Further, the two sites are almost but not totally independent of each other for binding, since abolishing one site does not prevent the amylose chain binding to the other site. Using AFM, we show that the amylose chains undergo a conformational change to form loops upon binding to the SBD, using either the recombinant wild-type SBD or a catalytically inactive mutant of GA-I. This characteristic conformation of amylose is lost when one of the SBD binding sites is eliminated by site-directed mutagenesis, as seen with the mutants W563 K or W590 K. Therefore, although each binding site is capable of simple binding to a ligand, both sites must be functional in order to induce a gross conformational change of the amylose molecules. Taken together these data suggest that for the complex with soluble amylose, SBD binds to a single amylose chain, site 1 being responsible for the initial recognition of the chain and site 2 being involved in tighter binding, leading to the circularisation of the amylose chain observed by AFM. Binding of the SBD to the amylose chain results in a novel two-turn helical amylose complex structure. The binding of parallel amylosic chains to the SBD may provide a basis for understanding the role of the SBD in facilitating enzymatic degradation of crystalline starches by glucoamylase 1.

Amino Acid Substitution↗
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

Arepas made from high amylose corn flour produce favorably low glucose and insulin responses in healthy humans.

The importance of the amylose: amylopectin ratio in the postprandial glycemic and insulinemic responses to corn was studied in food products that might realistically be consumed. Healthy subjects were given test meals in the form of arepas made from ordinary (25% amylose) or high amylose (70% amylose) corn flour. The ordinary corn meal contained 45 g of potentially available starch. To exclude the possible influence of a lowered content of potentially available starch due to formation of resistant starch in the high amylose product, this product was evaluated at two levels and included either on the basis of potentially available starch (45 g) or total starch (including resistant starch) (45 g, i.e., 29 g potentially available starch), respectively. The rate of starch hydrolysis, measured in vitro employing a method based on chewing, was studied. In addition, the content of in vitro resistant starch was analyzed in all products. The meals containing high amylose corn flour produced lower areas under the glucose and insulin response curves (57 and 42% lower, respectively) than did the meals containing ordinary cornmeal. This could not be explained by a lower amount of potentially available starch. No differences were noted when subjects consumed the two high amylose meals of arepas, despite 36% lower potentially available starch in one of the meals. The rate of starch hydrolysis measured in vitro was slower in the high amylose corn products than in the ordinary corn product. Resistant starch in the ordinary product was 3 g/100 g dry matter, vs. approximately 20 g/100 g dry matter in the high amylose products. We concluded that high amylose corn products have a potential to promote favorably low metabolic responses and high resistant starch contents.

Adult↗
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

Examination of number-average degree of polymerization and molar-based distribution of amylose by fluorescent labeling with 2-aminopyridine.

Suitable conditions for the fluorescent labeling of the reducing residue of amylose with 2-aminopyridine were examined. Amylose of up to 38.5 nmol was labeled with a constant labeling efficiency. The same efficiencies were obtained for amyloses having a number-average degree of polymerization (dpn) of 521-4400. The analysis of labeled amylose on size-exclusion HPLC with refractive index and fluorescence detection enabled the determination of dpn and dp distribution on a molar basis. The analysis of eight amylose specimens from seven botanical sources (potato, sweet potato, barley, wheat, indica rice, japonica rice, and maize) gave dpn values in good agreement with those determined by a conventional colorimetric method. The molar-based distributions of these amyloses were characteristic of botanical source and revealed the presence of several molecular species with different dp not detectable in the distribution on a weight basis. Small amyloses with a dp less than 10(3) were predominant in the cereals while amyloses with a dp over 10(3) were predominant in the tubers, suggesting a difference in the biosynthetic process determining the dp distribution of amylose between cereals and tubers.

Aminopyridines↗
PubMed2002

Plasma glucose and insulin reduction after consumption of breads varying in amylose content.

OBJECTIVE: Consumption of a meal high in amylose starch (70%) decreases peak insulin and glucose levels and area under the curve (AUC). The objective was to determine the amount of amylose necessary in a meal for the beneficial decrease in glucose or insulin to occur. DESIGN: Twenty-five subjects, 13 men (averaging 88.1 kg, 41 y, and 27.9 body mass index) and 12 women (averaging 72.4 kg, 41 y and 27.1 body mass index) were given six tolerance tests in a Latin Square design: glucose alone (1 g glucose/kg body weight) and five breads (1 g carbohydrate/kg body weight) made with 70% amylose cornstarch, standard cornstarch (30% amylose), and blends of the two starches (40, 50 and 60% amylose starch). A standard menu was fed for 3 days. One subject withdrew from the study. RESULTS: Glucose, insulin and glucagon response to the carbohydrate loads was similar in men and women. Peak glucose response was lowest after the breads containing 50-70% amylose starch. AUC was significantly higher after the glucose load than after all bread loads. The lowest AUCs occurred after the 60 and 70% amylose starch breads. Insulin response and AUC were significantly lower after the 60 and 70% amylose starch breads than after the glucose or the other breads. CONCLUSION: Results indicate that the amylose content of the starch used in the acute meal needs to be greater than 50% to significantly reduce plasma glucose and insulin in men and women.

Adult↗
PubMed2000

Hydrolytic action of alpha-amylase on high-amylose starch of low molecular mass.

High-amylose starches of low average degree of polymerization (d-p 61-71), formed as fine granules by interaction of Bacillus macerans cyclodextrin glucanotransferase with alpha-cyclodextrin (CD) at 2-70 degrees C, are highly insoluble in water and not gelatinizable under normal cooking conditions (100 degrees C). Samples of CD-derived starches, both cooked and uncooked, were subjected to hydrolysis in vitro by human salivary alpha-amylase at 37 degrees C under conditions chosen to resemble those in the human intestinal lumen. Released low-molecular-mass saccharides were determined quantitatively by HPLC and the results compared with those from similar studies with natural starches. Among uncooked starches, CD-derived starch showed very low reactivity towards alpha-amylase, along with potato starch and a high-amylose hybrid corn starch(64% amylose). Cooking greatly enhanced reactivity of natural starches, but only moderately increased reactivity of CD-derived starches. Susceptibility to hydrolysis of cooked starches increased in the following general order: CD-derived starch (approximately 100% amylose)<100%corn amylose (isolated by the butan-1-ol method)<hybrid high-amylose corn starch (64-66% amylose)<waxy maize starch (99-100%amylopectin) approximately ordinary corn starch ( approximately 25% amylose)<potato starch (approximately 25% amylose).

Amylose↗