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PubMed2005

Starch branching enzyme IIb in wheat is expressed at low levels in the endosperm compared to other cereals and encoded at a non-syntenic locus.

Studies of maize starch branching enzyme mutants suggest that the amylose extender high amylose starch phenotype is a consequence of the lack of expression of the predominant starch branching enzyme II isoform expressed in the endosperm, SBEIIb. However, in wheat, the ratio of SBEIIb and SBEIIa expression are inversely related to the expression levels observed in maize and rice. Analysis of RNA at 15 days post anthesis suggests that there are about 4-fold more RNA for SBE IIa than for SBE IIb. The genes for SBE IIa and SBE IIb from wheat are distinguished in the size of the first three exons, allowing isoform-specific antibodies to be produced. These antibodies were used to demonstrate that in the soluble fraction, the amount of SBE IIa protein is two to three fold higher than SBIIb, whereas in the starch granule, there is two to three fold more SBE IIb protein amount than SBE IIa. In a further difference to maize and rice, the genes for SBE IIa and SBE IIb are both located on the long arm of chromosome 2 in wheat, in a position not expected from rice-maize-wheat synteny.

1,4-alpha-Glucan Branching Enzyme↗

PubMed1999

The contribution of adenosine 5'-diphosphoglucose pyrophosphorylase to the control of starch synthesis in potato tubers

The aim of this work was to investigate the extent to which starch synthesis in potato (Solanum tuberosum L.) tubers is controlled by the activity of ADPglucose pyrophosphorylase (EC 2.7.7.27; AGPase). In order to do this, fluxes of carbohydrate metabolism were measured in tubers that had reduced AGPase activity as a result of the expression of a cDNA encoding the B subunit in the antisense orientation. Reduction in AGPase activity led to a reduction in starch accumulation, and an increase in sucrose accumulation. The control coefficient of AGPase on starch accumulation in intact plants was estimated to be around 0.3. The fluxes of carbohydrate metabolism were measured in tuber discs from wild-type and transgenic plants by investigating the metabolism of [U-(14)C]glucose. In tuber discs, the control coefficient of AGPase over starch synthesis was estimated as 0.55, while the control coefficient of the enzyme over sucrose synthesis was -0.47. The values obtained suggest that AGPase activity exerts appreciable control over tuber metabolism in potato.

Journal Article↗

PubMed1977

Inhibition of potato starch phosphorylase by alpha-D-glucopyranose-1,2-cyclic phosphate.

alpha-D-Glucopyranose-1.2-cyclic phosphate is a potent inhibitor of potato starch phosphorylase-catalyzed (1,4-alpha-D-glucan:orthophosphate alpha-glucosyltransferase, EC 2.4.1.1) starch elongation. The inhibition is competitive with respect to alpha-D-glucopyranose 1-phosphate (Glc-1-P) with Ki approximately 0.07 mM at pH 6.3 and 30 degrees C in 25 mM citrate buffer. The affinity of the phosphorylase - starch complex for the cyclic ester is therefore nearly 30 times as large as for Glc-1-P. Under conditions where alpha-D-glucopyranose-1,2-cyclic phosphate slows starch elongation by a factor of 3, UDPglucose, ADPglucose, D-glucose 6-phosphate, and D-glucose 2-phosphate cause rate reductions of less than 10%. The origin of the relatively strong binding of the cyclic ester to the phosphorylase, and its possible biological significance are discussed.

Adenosine Diphosphate Glucose↗

PubMed2000

Characterisation of the substituent distribution in hydroxypropylated potato amylopectin starch.

The distribution of substituents in hydroxypropylated potato amylopectin starch (amylose deficient) modified in a slurry of granular starch (HPPAPg) or in a polymer 'solution' of dissolved starch (HPPAPs), was investigated. The molar substitution (MS) was determined by three different methods: proton nuclear magnetic resonance (1H NMR) spectroscopy, gas-liquid chromatography (GLC) with mass spectrometry, and a colourimetric method. The MS values obtained by 1H NMR spectroscopy were higher than those obtained by GLC-mass spectrometry analysis and colourimetry. The relative ratio of 2-, 3-, and 6-substitution, as well as un-, mono-, and disubstitution in the anhydroglucose unit (AGU) were determined by GLC-mass spectrometry analysis. Results obtained showed no significant difference in molar distribution of hydroxypropyl groups in the AGU between the two derivatives. For analysis of the distribution pattern along the polymer chain, the starch derivatives were hydrolysed by enzymes with different selectivities. Debranching of the polymers indicated that more substituents were located in close vicinity to branching points in HPPAPg than in HPPAPs. Simultaneous alpha-amylase and amyloglucosidase hydrolysis of HPPAPg liberated more unsubstituted glucose units than the hydrolysis of HPPAPs, indicating a more heterogeneous distribution of substituents in HPPAPg.

Amylopectin↗

PubMed2001

High-performance anion-exchange chromatography-electrospray mass spectrometry for investigation of the substituent distribution in hydroxypropylated potato amylopectin starch.

The use of high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD) coupled on-line with electrospray mass spectrometry (ESI-MS) for analysis of the substitution pattern in chemically modified starch, has been investigated. In order to characterise the distribution of substitution groups along the polymer chain, hydroxypropylated potato amylopectin starch (HPPAP) was subjected to enzymic hydrolysis, followed by analysis of the degradation products by HPAEC-PAD-MS. When using conventional chromatographic techniques for characterisation of enzymic hydrolysates, standard compounds are required for identification of the hydrolysis products. However, the on-line coupling with ESI-MS allowed identification of all products obtained, substituted as well as unsubstituted, and also of those compounds that co-eluted, without the need for standards. Further, HPAEC-PAD-MS was shown to be useful for analysis of the substitution pattern in modified starch; from results obtained it was suggested that the hydroxypropyl groups were homogeneously distributed in the amylopectin molecule. It was also shown that the starch hydrolysing enzymes were hindered by the hydroxypropyl groups and preferentially cleaved glucosidic linkages between unsubstituted glucose units.

Amylopectin↗

PubMed2001

Chemistry and properties of starch based desiccants.

Desiccants currently used in industry include molecular sieves, lithium chloride, silica gel, and corn grits. Of these, only corn grits (a form of ground corn) are biodegradable and derived from a renewable resource. A major component of the corn grits, starch, is the primary adsorptive material in the corn grits. Other polysaccharides, including cellulose and hemicellulose also have adsorptive properties. The use of alpha-amylase (EC 3.2.1.1) to modify porosity and surface properties of starch resulted in materials with enhanced water sorption properties compared to the native material. This paper reviews the chemical and structural properties of starch, corn grits, and cellulose-based scaffolds on which starch can be affixed, in order to attain structures that might someday find uses in a range of desiccant applications for industrial, commercial, and residential processes.

Journal Article↗

PubMed2003

Development and characterization of aqueous amylose-rich maize starch dispersion for film formation.

Development and characterization of amylose-rich starch dispersion for film forming was performed. The influence of dispersion preparation temperature on amylose-rich maize starch (Hylon VII) film formation, and the physical properties of the films were investigated. The film-forming ability of the dispersions was evaluated with free films plasticized with glycerol and sorbitol, and the films were prepared at an elevated temperature (70 degrees C) by a casting technique. The solid-state and particle properties of dispersions were investigated by means of X-ray diffraction (XRD), Fourier transform near infrared (FT-NIR) spectroscopy and laser diffraction particle size analysis. Free films were characterized with respect to their appearance, by FT-NIR spectroscopy, and by XRD. Mechanical stress-strain properties were also studied. Increasing the temperature of dispersion preparation results in higher crystallinity, thus affecting the film forming ability. Mechanically strong and elastic films can be formed from amylose-rich starch dispersion formed at 40 degrees C. The more crystalline precipitate complex (obtained at 80 degrees C) and the entirely amorphous gel (obtained at 10 degrees C) formed non-continuous and cloudy films. The better film-forming properties of the dispersion formed at 40 degrees C are probably due to the highly amorphous structure and smaller particle size. The study shows the possibility of using ambient tempered amylose-starch dispersion for film forming.

Amylose↗

PubMed1999

Starch particles modified with gelatin as novel small carriers for mammalian cells.

Promotion of cell aggregation by addition of small starch particles with and without modification with gelatin was investigated, and the influence of CHO cell aggregation by the addition of modified starch on substrate consumption and production of tissue plasminogen activator (tPA) was investigated. Addition of starch particles (approximately 10 micromPhi) covalently bonded with gelatin was very effective in forming cell aggregates ranging from 100 to 300 microm in diameter and decreased the cell sedimentation time to one-thirtieth that of the normal time. There was almost no influence of the addition of modified starch particles on cell metabolism and tPA production. Cell aggregation makes it easy to separate cells from culture during changing of medium in a cell suspension culture without the use of special equipment, such as centrifuges, hollow fiber membranes, and spin filters.

Journal Article↗

PubMed1998

Structural Modification and Bioavailability of Starch Components As Related to the Extent of Maillard Reaction: An Enzymatic Degradation and a Solid-State (13)C CPMAS NMR Study.

Starch and starch components, amylose and amylopectin, from potato, have been studied in order to understand the modifications, induced by different levels of the Maillard reaction occurring in the presence of amino acids (L-lysine in this study), in the macromolecular structure and digestibility. Structural characterization was performed by (13)C CPMAS NMR, and differences in the bioavailability of these polymers were studied by enzymatic degradation kinetics. Results obtained reveal that changes are induced by the Maillard reaction, whose occurrence has been verified and measured by the furosine (epsilon-N-2-furoylmethyl-L-lysine) evaluation, on the macromolecular structure of starchy materials and on their enzymatic susceptibility. Lysine seems to act as a disordering agent; a loss of crystallinity is evident for starch and amylopectin and, in particular, for amylose. Finally, within the same sample, as the lysine concentration increases, the polymer digestibility decreases, confirming that structural organization is not the only determinant of starch digestibility.

Journal Article↗

PubMed2001

Sprouting of the fructan- and starch-storing geophyte Lachenalia minima: Effects on carbohydrate and water content within the bulbs.

The carbohydrate pool within the bulbs of Lachenalia minima W.F. Barker (Hyacinthaceae) consists of similar amounts of fructans and starch. This study was conducted to examine the changes within the pool of non-structural carbohydrates that occur during sprouting under field conditions. The bulbs were watered over a period of 23 days to simulate the onset of the rainy season. Even though there was no significant change of the total fructan content, the distribution and the composition of the fructan fraction within the different leaf scales of the bulbs altered during sprouting. The major changes occurred in the innermost scales, the total fructan content increased from 300 (day 0) to 607 (day 23) g kg-1 dry mass and high-performance anion-exchange chromatography analysis revealed a significant increase of fructans with low degree of polymerization (DP). With respect to starch, the most pronounced difference accompanying the transition to growth was also in the innermost scales. In contrast to fructans, starch content decreased from 241 (day 0) to 60 (day 14) g kg-1 dry mass. These results demonstrate that starch, and not fructan, is used as the carbon and energy source for sprouting. The water content data suggest the involvement of fructans in water relations. The preferential accumulation of low DP fructans and sucrose within the innermost scales directs the water flow to where it is most needed for growth. Similar changes were obtained for bulbs in the dry soil, but transformation rates were much slower and occurred to a lesser extent, indicating that these reactions were not triggered but were accelerated by water.

Journal Article↗

PubMed1992

Determination of dietary fibre as non-starch polysaccharides by gas-liquid chromatography.

An improved method is described for the measurement of total, soluble and insoluble dietary fibre as non-starch polysaccharides (NSP). An established procedure is modified to allow more rapid removal of starch and hydrolysis of NSP. In its present form the procedure is simpler and more robust than those previously published. In the modified method starch is removed enzymically within 50 min and NSP is precipitated with ethanol and then hydrolysed by treatment with sulfuric acid for 2 h. The constituent sugars can in turn be measured by gas-liquid chromatography, high-performance liquid chromatography or more rapidly by colorimetry. The improved procedure described here for the removal of starch and hydrolysis of NSP applies to all three techniques, but only the method for measurement of sugars by gas-liquid chromatography is described here in full.

Chromatography, Gas↗

PubMed2003

The maltase-glucoamylase gene: common ancestry to sucrase-isomaltase with complementary starch digestion activities.

Brush-border maltase-glucoamylase (MGA) activity serves as the final step of small intestinal digestion of linear regions of dietary starch to glucose. Brush-border sucrase-isomaltase (SI) activity is complementary, through digestion of branched starch linkages. Here we report the cloning and sequencing of human MGA gene and demonstrate its close evolutionary relationship to SI. The gene is approximately 82,000 bp long and located at chromosome 7q34. Forty-eight exons were identified. The 5' gene product, when expressed as the N-terminal protein sequence, hydrolyzes maltose and starch, but not sucrose, and is thus distinct from SI. The catalytic residue was identified by mutation of an aspartic acid and was found to be identical with that described for SI. The exon structures of MGA and SI were identical. This homology of genomic structure is even more impressive than the previously reported 59% amino acid sequence identity. The shared exon structures and peptide domains, including proton donors, suggest that MGA and SI evolved by duplication of an ancestral gene, which itself had already undergone tandem gene duplication. The complementary human enzyme activities allow digestion of the starches of plant origin that make up two-thirds of most diets.

Animals↗

PubMed2002

Differential characteristics and subcellular localization of two starch-branching enzyme isoforms encoded by a single gene in Phaseolus vulgaris L.

Starch-branching enzymes (SBE) have a dominant role for amylopectin structure as they define chain length and frequency of branch points. We have previously shown that one of the SBE isoforms of kidney bean (Phaseolus vulgaris L.), designated PvSBE2, has a molecular mass (82 kDa) significantly smaller than those reported for isologous SBEs from pea (SBEI), maize (BEIIb), and rice (RBE3). Additionally, in contrast to the dual location of the pea SBEI in both the soluble and starch granule fractions, PvSBE2 was found only in the soluble fraction during seed development. Analysis of a pvsbe2 cDNA suggested that PvSBE2 is generated from a larger precursor with a putative plastid targeting sequence of 156 residues. Here we describe the occurrence of a larger 100-kDa form (LF-PvSBE2) of PvSBE2 found both in the soluble and starch granule fractions of the developing seeds. The determined N-terminal sequence, VKSSHDSD, of LF-PvSBE2 corresponded to a peptide sequence located 111 amino acids upstream from the N terminus of purified PvSBE2, suggesting that LF-PvSBE2 and PvSBE2 are products of the same gene. Analysis of the products by 5'-RACE (rapid amplification of cDNA ends) and reverse transcription PCR indicated that the two transcripts for pre-LF-PvSBE2 and pre-PvSBE2 are generated by alternative splicing. Recombinant LF-PvSBE2 (rLF-PvSBE2) was purified from Escherichia coli and the kinetic properties were compared with those of recombinant PvSBE2 (rPvSBE2). rLF-PvSBE2 had much higher affinity for amylopectin (K(m) = 4.4 mg/ml) than rPvSBE2 (18.4 mg/ml), whereas the V(max) of rLF-PvSBE2 (135 units/mg) for this substrate was much lower than that of rPvSBE2 (561 units/mg). These results suggest that the N-terminal extension of LF-PvSBE2 plays a critical role for localization in starch granules by altering its enzymatic properties.

1,4-alpha-Glucan Branching Enzyme↗

PubMed1999

Effects of a xylanase on individual bird variation, starch digestion throughout the intestine, and ileal and caecal volatile fatty acid production in chickens fed wheat.

1. The effects of a xylanase on digesta viscosity and starch digestibility throughout the small intestine and volatile fatty acid production in the ileum and caeca were investigated in broilers fed on a low-metabolisable energy wheat diet. 2. The xylanase reduced (P<0.01) duodenal (2.9 vs. 1.7), jejunal (4.6 vs. 2.3) and ileal (14.0 vs. 3.9) digesta viscosities (mPas) and increased AME (P<0.01) of the wheat and starch digestibility (P<0.5) in the jejunum and ileum. Between-bird variability in ME and digestibility of starch was also reduced. 3. Enzyme supplementation reduced (P<0.05) fermentation in the ileum, but increased (P<0.05) it in the caeca. 4. The anti-nutritive effect of soluble non-starch polysaccharides (NSP) is related to their ability to increase digesta viscosity along the gut; this in turn causes changes in gut microflora and efficiency of nutrient utilisation by the chicken. Use of appropriate enzymes is an effective way of dealing with grains with high NSP content in poultry diets.

Animal Feed↗

PubMed2000

Gastrointestinal symptoms rating scale in coeliac disease patients on wheat starch-based gluten-free diets.

BACKGROUND: A wheat starch-based gluten-free diet is widely adopted in the treatment of coeliac disease, even though the products contain trace amounts of gluten. The aim here was to establish whether such a diet sustains abdominal symptoms. METHODS: The Gastrointestinal Symptom Rating Scale (GSRS) was applied to 58 coeliac disease patients on gluten-free diets and 110 non-coeliac controls. An estimate was made of daily dietary fibre and wheat starch-derived gluten. Psychological well-being was evaluated by a structured interview. Twenty-three coeliac patients consented to small-bowel biopsy. RESULTS: The mean GSRS score in coeliac disease patients did not differ from that in control subjects. Poorer psychological well-being was associated with abdominal symptoms in coeliac patients, whereas the daily amount of wheat starch had no effect on GSRS score. Overall dietary compliance was good, and villous atrophy was found in only 2 out of 23 patients. The average fibre consumption, 13 g per day, was lower than recommended. CONCLUSIONS: Wheat starch-based gluten-free products are well-tolerated in coeliac disease patients, provided that their diets are otherwise strict.

Adult↗

PubMed1985

[Effect of type of starch and quantity in rations on apparent and true digestibility of nitrogen and nitrogen balance in sheep].

In a digestibility trial 5 semisynthetic rations were fed in 3 periods to 10 male sheep to examine the effects on N balance, components of faecal nitrogen and N digestibility. The rations contained constant amounts of nitrogen but different contents of cellulose and two different types of starch (untreated and steamflaked). Content and type of starch did not show any noticeable effect neither on excretion of undigested dietary nitrogen nor on true digestibility. There could not be noticed any effects on the apparent N digestibility by changing contents of cellulose or untreated starch. If the rations contained steamflaked corn starch, the animals excreted more faecal nitrogen and therefore showed a lower apparent N digestibility. Especially the water soluble N fraction of the faecal nitrogen was clearly higher. Compensation took place through a lower N excretion with the urine. The reason for increased faecal N excretion may be higher microbial protein synthesis in the rumen. This was accented by the allantoin excretion with the urine.

Animal Feed↗

PubMed1990

[Measuring of the energy turnover in adult swine during feeding of rations with potato starch, potatoes, beets, pressed shreds and coarse fodder as supplements to a basic ration. 2. Evaluation and discussion of the results for further development of energetic feed rating for swine].

Energy metabolism measurings of male castrates of a live weight between 90 and 180 kg after feeding rations with a wide variety in the content of various carbohydrates (crude fibre 36-185, water soluble carbohydrates 25-306, starch 272-683 g/kg DM) formed the experimental basis of the considerations. Energy retention depended significantly on the digestibility and metabolizability of the energy, on energy concentration and the crude fibre content of the rations. By means of multiple regression analyses the energetic effect of 1 g digested matter of the carbohydrate fraction was assessed as follows: 12.9 kJ for starch, 12.1 kJ for disaccharides, 11.5 kJ for the remaining water soluble carbohydrates and 10.4 kJ for bacterially fermentable carbohydrates (BFC). There was a difference between the energetic effective value of starch and BFC. This corresponds completely to the difference in the utilization of metabolizable energy between exclusively precaecal and postileal digestion. The following conclusions are drawn for the further development of the energetic feed evaluation for pigs in the framework of the GDR feed evaluation system: --There are to be differentiated fixed values for the retention of digestible carbohydrates for the fractions starch, water soluble carbohydrates (pectin) and bacterially fermentable carbohydrates. --The influence of the digestibility of the energy in the ration on the energetic retention effect of BFC is small. The integration of these variables into an estimation equation for the energetic feed value is therefore not necessary.

Animal Feed↗

PubMed1988

Effect of starch structure on glucose and insulin responses in adults.

Twelve women and 13 men were given meals containing cornstarch with 70% of the starch in the form of amylopectin or amylose to determine if differences in glycemic response result from different chemical structure. Blood was drawn before and 30, 60, 120, and 180 min after each meal. The meals consisted of starch crackers fed at the rate of 1 g carbohydrate from starch per kilogram body weight. The amylose meal resulted in a significantly lower glucose peak at 30 min than did the amylopectin meal. Plasma insulin response was significantly lower 30 and 60 min after amylose than after the amylopectin meal. Summed insulin above fasting was significantly lower after amylose while summed glucose was not significantly different between the two meals. The sustained plasma glucose levels after the amylose meal with reduced insulin requirement suggest amylose starch may be of potential benefit to carbohydrate-sensitive or diabetic individuals.

Adult↗