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At least 19 recordsLinked to original sources
PubMed1996

Physical association of starch biosynthetic enzymes with starch granules of maize endosperm. Granule-associated forms of starch synthase I and starch branching enzyme II.

Antibodies were used to probe the degree of association of starch biosynthetic enzymes with starch granules isolated from maize (Zea mays) endosperm. Graded washings of the starch granule, followed by release of polypeptides by gelatinization in 2% sodium dodecyl sulfate, enables distinction between strongly and loosely adherent proteins. Mild aqueous washing of granules resulted in near-complete solubilization of ADP-glucose pyrophosphorylase, indicating that little, if any, ADP-glucose pyrophosphorylase is granule associated. In contrast, all of the waxy protein plus significant levels of starch synthase I and starch branching enzyme II (BEII) remained granule associated. Stringent washings using protease and detergent demonstrated that the waxy protein, more than 85% total endosperm starch synthase I protein, and more than 45% of BEII protein were strongly associated with starch granules. Rates of polypeptide accumulation within starch granules remained constant during endosperm development. Soluble and granule-derived forms of BEII yielded identical peptide maps and overlapping tryptic fragments closely aligned with deduced amino acid sequences from BEII cDNA clones. These observations provide direct evidence that BEII exits as both soluble and granule-associated entities. We conclude that each of the known starch biosynthetic enzymes in maize endosperm exhibits a differential propensity to associate with, or to become irreversibly entrapped within, the starch granule.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1998

The effect of potato starch derived and corn starch derived hydroxyethyl starch on in vitro blood coagulation.

We have compared the effects of progressive in vitro haemodilution (30% and 60%) with potato starch derived hydroxyethyl starch and corn starch derived hydroxyethyl starch on blood coagulation in 80 patients using thrombelastography. Both solutions significantly compromised blood coagulation as evidenced by an increase in coagulation time and decrease in angle alpha, maximum amplitude and coagulation index (p < 0.05). Blood coagulation was more compromised during haemodilution with potato starch derived hydroxyethyl starch as compared with corn starch derived hydroxyethyl starch (p < 0.05). When taking the effect of haemodilution with 0.9% saline into account, haemodilution with both hydroxyethyl starch solutions also augmented clot lysis (p < 0.05), with potato starch derived hydroxyethyl starch having a greater effect than corn starch derived hydroxyethyl starch (p < 0.05). We conclude that potato starch derived hydroxyethyl starch compromises in vitro blood coagulation more than corn starch derived hydroxyethyl starch.

Adult↗
PubMed1978

Comparative susceptibility to amylases of starch granules of several single endosperm mutants representative of floury-opaque, starch-deficient, and modified starch types and their double-mutant combinations with opaque-2 in four inbred lines of maize.

Starch granules were prepared from kernels of eight single endosperm mutants, brittle-1, (bt1), brittle-2 (bt2), floury-1, floury-2, soft starch, opaque-1 (o1), shrunken-2 (sh2), and sugary-2 (su2), and their double-mutant combinations with opaque-2 (o2) of four inbred lines of maize (Zea mays L.), B37, C103, Oh43 and W64A. We compared the susceptibility of various starch granules to Rhizopus glucoamylase and pancreatin. Starch granules of the su2 and su2o2 mutants were digested by amylases much faster than those of the normal counterparts. Starch granules of the bt1, bt2, o1 and sh2 mutants tended to be digested by amylases faster than those of normal maize. Starch granules of double-mutant combinations with the o2 gene were, in general, digested to an extent very comparable to their respective non-opaque single mutant counterparts in each of their four inbred backgrounds. We followed the relative digestion of starch granules by using scanning electron microscopy. Starch granules of endosperm mutants susceptible to amylases showed numerous pin holes on the surface layer and the pores penetrated into the inner layers of the granules during the attack by amylases. In some of the granules the inner portion, which appeared terraced or step-shaped, could be seen. This may be indicative of layered internal structures of the granules.

Amylases↗
PubMed2000

New type of starch-binding domain: the direct repeat motif in the C-terminal region of Bacillus sp. no. 195 alpha-amylase contributes to starch binding and raw starch degrading.

The alpha-amylase from Bacillus sp. no. 195 (BAA) consists of two domains: one is the catalytic domain similar to alpha-amylases from animals and Streptomyces in the N-terminal region; the other is the functionally unknown domain composed of an approx. 90-residue direct repeat in the C-terminal region. The gene coding for BAA was expressed in Streptomyces lividans TK24. Three active forms of the gene products were found. The pH and thermal profiles of BAAs, and their catalytic activities for p-nitrophenyl maltopentaoside and soluble starch, showed almost the same behaviours. The largest, 69 kDa, form (BAA-alpha) was of the same molecular mass as that of the mature protein estimated from the nucleotide sequence, and had raw-starch-binding and -degrading abilities. The second largest, 60 kDa, form (BAA-beta), whose molecular mass was the same as that of the natural enzyme from Bacillus sp. no. 195, was generated by proteolytic processing between the two repeat sequences in the C-terminal region, and had lower activities for raw starch binding and degrading than those of BAA-alpha. The smallest, 50 kDa, form (BAA-gamma) contained only the N-terminal catalytic domain as a result of removal of the C-terminal repeat sequence, which led to loss of binding and degradation of insoluble starches. Thus the starch adsorption capacity and raw-starch-degrading activity of BAAs depends on the existence of the repeat sequence in the C-terminal region. BAA-alpha was specifically adsorbed on starch or dextran (alpha-1,4 or alpha-1,6 glucan), and specifically desorbed with maltose or beta-cyclodextrin. These observations indicated that the repeat sequence of the enzyme was functional in the starch-binding domain (SBD). We propose the designation of the homologues to the SBD of glucoamylase from Aspergillus niger as family I SBDs, the homologues to that of glucoamylase from Rhizopus oryzae as family II, and the homologues of this repeat sequence of BAA as family III.

Adsorption↗
PubMed1993

Soluble isoforms of starch synthase and starch-branching enzyme also occur within starch granules in developing pea embryos.

Developing wild-type pea embryos contain two major isoforms of starch synthase and two isoforms of starch-branching enzyme. One of the starch synthases and both starch-branching enzymes occur both in the soluble fraction and tightly bound to starch granules. The other starch synthase, which is very similar to the waxy proteins of other species, is exclusively granule-bound., It is inactive when solubilized in a native form from starch granules, but activity is recovered when the SDS-denatured protein is reconstituted from polyacrylamide gels. Evidence is presented which indicates that all of these proteins become incorporated within the structure of the granule as it grows. It is proposed that the granule-bound waxy protein is active in vivo at the granule surface, whereas the remaining proteins are active in the soluble fraction of the amyloplast. The proteins become trapped within the granule matrix as the polymers they synthesize crystallize around them, and they probably play no further part in polymer synthesis.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1989

Biochemical evidence that starch breakdown by Bacteroides thetaiotaomicron involves outer membrane starch-binding sites and periplasmic starch-degrading enzymes.

Bacteroides thetaiotaomicron can utilize amylose, amylopectin, and pullulan as sole sources of carbon and energy. The enzymes that degrade these polysaccharides were found to be primarily cell associated rather than extracellular. Although some activity was detected in extracellular fluid, this appeared to be the result of cell lysis. The cell-associated amylase, amylopectinase, and pullulanase activities partitioned similarly to the periplasmic marker, acid phosphatase, when cells were exposed to a cold-shock treatment. Two other enzymes associated with starch breakdown, alpha-glucosidase and maltase, appeared to be located in the cytoplasm. Intact cells of B. thetaiotaomicron were found to bind 14C-starch. Binding was probably mediated by a protein because it was saturable and was decreased by treatment of cells with proteinase K. Results of competition experiments showed that the starch-binding proteins had a preference for maltodextrins larger than maltohexaose and a low affinity for maltose and maltotriose. Both the degradative enzymes and starch binding were induced by maltose. These findings indicate that starch utilization by B. thetaiotaomicron apparently does not involve secretion of extracellular enzymes. Rather, binding of the starch molecule to the cell surface appears to be a first step to passing the molecule through the outer membrane and into the periplasmic space.

Bacterial Outer Membrane Proteins↗
PubMed1993

Starch Degradation and Distribution of the Starch-Degrading Enzymes in Vicia faba Leaves (Diurnal Oscillation of Amylolytic Activity and Starch Content in Chloroplasts).

Subcellular localization of the starch-degrading enzymes in Vicia faba leaves was achieved by an electrophoretic transfer method through a starch-containing gel (SCG) and enzyme activity measurements. Total amylolytic and phosphorolytic activities were found predominantly in the extrachloroplastic fraction, whereas the debranching enzymes showed homogenous distribution between stromal and extrachloroplastic fractions. Staining of end products in the SCG revealed two isoforms of [alpha]-amylase (EC 3.2.1.1) and very low [beta]-amylase activity (EC 3.2.1.2) in the chloroplast preparation, whereas [alpha]- and [beta]-amylase exhibited higher activities in the crude extract. However, it is unclear whether the low [alpha]- and [beta]-amylase activities associated with the chloroplast are contamination or activities that are integrally associated with the chloroplast. Study of the diurnal fluctuation of the starch content and of the amylase activities under a 9-h/15-h photoperiod showed a 2-fold increase of the total amylolytic activity in the chloroplasts concurrent with the starch degradation in the dark. No fluctuation was detectable for the extrachloroplastic enzymes. The possible roles and function of the chloroplastic and extrachloroplastic hydrolytic enzymes are discussed.

Journal Article↗
PubMed2002

Association of alpha-amylase and the R1 protein with starch granules precedes the initiation of net starch degradation in turions of Spirodela polyrhiza.

In turions of Spirodela polyrhiza (L.) Schleiden, net degradation of storage starch is controlled by a special low fluence response of phytochrome requiring illumination for several days. This light effect has been used to study protein-starch interactions that occur prior to and during net degradation of starch. Following various pretreatments on S. polyrhiza turions, native starch granules were isolated and two fractions of starch-related proteins were distinguished: proteins enclosed within the starch particles (starch-internalized proteins) and those attached to the surface (starch-associated proteins). The pattern of starch-associated proteins as resolved by SDS-PAGE was more complex than that of starch-internalized proteins and varied depending upon the pretreatment of the turions. Two starch associated proteins were identified immunochemically as alpha-amylase (EC 3.2.1.1) and the R1 protein (Lorberth et al. (1998) Nature Biotechnology 16: 473-477). Dark-pretreatment of non-dormant turions does not induce starch net degradation. Under these conditions, alpha-amylase and R1 were bound to the surface of the starch granules. Continuous illumination with red light induces a rapid degradation of starch. Within the first 24 h of illumination the level of starch-associated alpha-amylase transiently increased and subsequently decreased rapidly. Similarly, the amount of the starch-associated R1 also decreased during illumination. The dissociation of both alpha-amylase and R1 from the starch granules preceded the decrease in starch content. However, binding of the two proteins to starch granules remained unchanged when the turions did not perform net starch degradation (as observed during continuous darkness, orthophosphate deficiency, or dormancy of the turions). Thus, during net starch degradation, so far unidentified changes are postulated to occur at the surface of the starch particles that are relevant for protein binding. This conclusion was supported by in vitro studies in which the binding of purified beta-amylase (EC 3.2.1.2) to starch granules isolated from turions following various pretreatments was monitored. The enzyme did bind to starch granules prepared from dark-stored turions (in which starch degradation had not been initiated), but not to those isolated from illuminated (starch degrading) turions.

Journal Article↗
PubMed1992

Is starch flavor unitary? Evidence from studies of cooked starch.

Although starch is the world's most abundant nutritive carbohydrate, its sensory properties are not as well understood as those of sugars. Previous researchers have assumed that all starches have the same flavor. The present experiments examined flavor differences among starches. Untrained rats were offered a choice of suspensions containing raw versus cooked starch. For some starches (potato and rice), rats strongly preferred cooked over uncooked starch. For other starches (regular corn, corn amylopectin, and wheat), rats showed little or no preference for cooked over uncooked starch. In order to determine whether the greater preference for cooked starch reflects a difference in flavor intensity, rats were conditioned to avoid potato or corn amylopectin starches by pairing ingestion of these substances with lithium chloride injections. Rats trained to avoid raw starch also avoided cooked starch, indicating that cooked and raw starch have similar flavors. However, when these trained rats were offered a choice between cooked and raw starch, they avoided the raw starch; this result is inconsistent with the assumption that cooking enhances the intensity of starch flavor. Similar results were obtained with corn amylopectin and potato starch, even though these starches differ greatly with regard to the effects of cooking on preference in untrained rats. However, rats trained to avoid potato starch avoided this starch to a greater degree than did rats trained to avoid corn amylopectin; conversely, rats trained to avoid corn amylopectin avoided this starch to a greater degree than did rats trained to avoid potato starch. Therefore, the flavor of starch is complex; there are specific flavor notes related to species and cooking.(ABSTRACT TRUNCATED AT 250 WORDS)

Amylopectin↗
PubMed1993

Dietary native resistant starch but not retrograded resistant starch raises magnesium and calcium absorption in rats.

The effects on calcium and magnesium absorption of dietary native and retrograded cornstarch were studied in rats. Uncooked high amylose starch granules (35% of total glucose equivalents as enzyme-resistant starch) and cooked and cooled (-20 degrees C) high amylose starch (24% of total glucose equivalents as retrograded resistant starch) were used as test starches, and cooked normal starch (3% of total glucose equivalents as resistant starch) was used as control starch. Native vs. control starch raised the amount of polymerized glucose in ileum, but not in feces. Retrograded starch produced more polymerized glucose than control starch in both ileum and feces. When compared with control starch, ileal pH was significantly lowered by native starch and tended to be raised by retrograded starch. Cecal pH was lowered by the two preparations rich in resistant starch. Apparent absorption of calcium and magnesium was raised by native starch but not by retrograded resistant starch. Calcium concentrations in the liquid phase of the ileum tended to be elevated by native starch but were significantly lowered by retrograded starch relative to control starch. Magnesium and calcium concentrations in liquid cecal contents tended to be raised with native starch; they were unchanged with retrograded starch. It is suggested that native resistant starch raised calcium and magnesium absorption because it tended to enhance the solubility of these minerals in ileal and cecal digesta.

Absorption↗
PubMed2001

In vitro starch digestion correlates well with rate and extent of starch digestion in broiler chickens.

Current feed evaluation systems for poultry are based on digested components (fat, protein and nitrogen-free extracts). Digestible starch is the most important energy source in broiler chicken feeds and is part of the nitrogen-free extract fraction. Digestible starch may be predicted using an in vitro method that mimics digestive processes in the gastrointestinal tract of broiler chickens. An experiment was designed to use this method for predicting site, rate and extent of starch digestion in broiler chickens. In vitro starch digestion was studied in 12 experimental diets differing in starch sources. These diets were also used in a digestibility trial with broiler chickens. Correlations between in vitro and in vivo starch digestion were calculated. Starch digestion after 2 h incubation correlated well with in vivo starch digestion in the first half of the small intestine (r = 0.94). A 4-h incubation period resulted in a good correlation between in vitro starch digestion and ileal starch digestion (r = 0.96). In vitro starch digestion rate (h(-1)) correlated well with in vivo starch digestion rate (r = 0.87). In vitro starch digestion of individual starch sources was additive. It appeared that legume seeds and waxy corn contained two starch fractions, which were digested at different rates. We conclude that starch digestion rate in broiler chickens is well predicted by the in vitro method.

Animal Feed↗
PubMed2001

Effect of starch application into the proximal duodenum of ruminants on starch digestibility in the small and total intestine.

Four Slovakian Black-and-white bulls (LW 410 +/- 12 kg; Exp. 1) and four Slovakian Black-and-white non lactating dairy cows (LW 475 +/- 14 kg; Exp. 2) with permanent ruminal cannulas, duodenal T-cannulas and ileal re-entrant cannulas were used in a 4 x 4 Latin square design to determine the postruminal capacity of starch digestion. In Exp. 1 bulls received 5.4 kg DM from corn silage and 3.6 kg DM from alfalfa hay, in Exp. 2 cows consumed only 2.1 kg DM corn silage and 1.9 kg DM alfalfa hay. Additionally, either 750 or 1500 g (Exp. 1) or resp. 1000 or 2000 g (Exp. 2) gelatinized corn or wheat starch per animal and day were applied as pulse doses or as infusion into the proximal duodenum. In both experiments the duodenal and ileal nutrient flow, as well as the faecal excretion without starch application, were measured in a pre-period. After starting starch application ileal digesta and faeces were sampled over 120 h after 9 or 23 days of adaptation respectively. Cr2O3 was used as a flow marker. It was shown, that the capacity of starch utilisation in the small intestine was limited. The effect of different doses of bypass-starch was more pronounced than the effect of different starch sources. Starch digestibility decreased with increasing amounts of starch in the intestine (Exp. 1: corn starch: from 74.3 to 68.0%, P < 0.001; wheat starch: from 76.7 to 67.4%, P < 0.001; Exp. 2: corn starch: from 71.4 to 50.3%. P < 0.001; wheat starch: from 73.8 to 53.1%, P < 0.001). Corn starch was 0.6 to 2.4% units (P < 0.05) and 2.4 to 2.8% units (P < 0.001) less digested than wheat starch in Exp. 1 and Exp. 2, respectively.

Animal Feed↗
PubMed2003

Estimates of starch digestion in the rat small intestine differ from those obtained using in vitro time-sensitive starch fractionation assays.

The objectives of this study were as follows: 1) to determine the rate and extent of starch disappearance from the small intestine of the rat fed selected starch sources, 2) to determine the ratios of the major starch fractions [rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS)] in those starch sources using two in vitro methods and 3) to compare the two data sets to determine the accuracy of the in vitro methods. Diets were prepared using cornstarch, potato starch, amylomaize, maltodextrin, modified maltodextrin or pullulan. Starch sources and diets were analyzed for starch fractions by two in vitro methods. Diets were fed to rats, intestinal contents were collected and the ethanol-induced precipitate from the contents was analyzed to obtain a digestion curve that was mathematically modeled for comparison to results obtained using the two in vitro methods. Only the cornstarch diet had a defined amount of RDS, SDS and RS. The RDS concentration obtained from the intestinal contents of the rats fed the cornstarch diet differed (P < 0.05) from that determined by one in vitro method but was consistent with the value obtained using the other in vitro method. All other digestible starch values obtained differed (P < 0.05) among methods except for that of amylomaize. Starch fractions in starch sources obtained using in vitro procedures differed (P < 0.05) from values obtained for diets. The rate of disappearance differed (P < 0.05) between in vivo and in vitro procedures. There was minimal agreement between in vitro methods tested, and there was also minimal agreement between in vitro and in vivo results. Classification of starch into RDS and SDS components cannot be accomplished for a variety of starch sources, with cornstarch being the major exception.

Animals↗
PubMed1993

Starch bioavailability in arepas made from ordinary or high amylose corn: concentration and gastrointestinal fate of resistant starch in rats.

The purpose of the present investigation was to study the importance of the amylose/amylopectin ratio for the content and gastrointestinal fate of resistant starch in a realistic composite starchy food. Corn-based breads (arepas) from dent corn (25% amylose) and from high amylose corn (70% amylose) were used as test products. Resistant starch concentration was evaluated in vitro and in vivo using rats treated with an antibiotic drug (Nebacitin) to suppress hindgut fermentation. Experiments in rats with intact hindgut microflora allowed determination of resistant starch fermentability. The small intestinal digestibility of starch in dent corn arepas was close to 96% (total starch basis), whereas the starch in high amylose arepas was poorly digested (approximately 68%, total starch basis), as calculated from the fecal recovery of resistant starch in Nebacitin-treated animals. The main resistant starch fraction required solubilization in alkali to render it available to the analytical amylases (nonhydrated fraction). The total amount of resistant starch as well as the nonhydrated starch fraction delivered to the hindgut could be accurately predicted from analysis of starch remnants in an enzymatic gravimetric dietary fiber residue. Resistant starch present in dent corn arepas was fermented approximately 63%, whereas the fermentability of resistant starch from the high amylose product was remarkably low (< 11%).

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↗
PubMed1994

Starch Phosphorylation in Potato Tubers Proceeds Concurrently with de Novo Biosynthesis of Starch.

The in vivo phosphorylation of starch was studied in Solanum tuberosum cv Dianella and Posmo. Small starch granules contain 25% more ester-bound phosphate per glucose residue than large starch granules. The degree of phosphorylation was found to be almost constant during tuber development. Isolated tuber discs synthesize starch from externally supplied glucose at a significant rate. Tuber discs supplied with glucose and [32P]orthophosphate incorporate radiolabeled phosphorus into the starch. The level of 32P incorporation is proportional to the amount of starch synthesized. The incorporation of 32P from orthophosphate is correlated to de novo synthesis of starch, since the incorporation of 32P is diminished upon inhibition of starch synthesis by fluoride. Based on the amount of [14C]glucose phosphate isolated after hydrolysis of purified starch from tuber discs incubated in the presence of [U-14C]glucose, approximately 0.5% of the glucose residues of the de novo-synthesized starch are phosphorylated. This value is in general agreement with the observed levels of phosphorus in starch accumulated during tuber development. Thus, the enzyme system responsible for starch phosphorylation is fully active in the isolated tuber discs, and the starch phosphorylation proceeds as an integrated part of de novo starch synthesis.

Journal Article↗
PubMedDate not supplied

Improved adsorption to starch of a beta-galactosidase fusion protein containing the starch-binding domain from Aspergillus glucoamylase.

We have previously shown (Chen et al., 1991) that a beta-galactosidase (beta-gal) fusion protein (BSB133) containing 133 amino acids (aa) from the C-terminus of Aspergillus glucoamylase (GA) adsorbs strongly to starch compared to beta-gal, due to the presence of the GA starch-binding domain. We have now made deletions at the N-terminus of this 133-aa region to test the minimal size required for starch binding of beta-gal fusion proteins. Three fusion proteins (BSB119, BSB103, and BSB80) were genetically engineered, containing 119, 103, and 80 C-terminal aa from GA, respectively. The fusion proteins were expressed in Escherichia coli and purified. Purified BSB119 adsorbed to native starch at least 2-fold more strongly than did BSB133 or fusion proteins with shorter tails. Adsorption isotherms generated over a wide range of initial concentrations indicated a 10-fold difference in the loading capacity of starch for BSB119 (36.5 mg of protein/g of starch) compared to beta-gal (3.7 mg of protein/g of starch). Adsorption constants calculated from the initial slopes of the isotherms indicated a nearly 30-fold difference in affinity to starch for BSB119 (Kad = 63 mL/g of starch) compared to beta-gal (Kad = 2.3 mL/g of starch). BSB119 in the presence of crude enzyme extracts also bound to starch with a high affinity compared to a beta-gal control. Potential applications of the starch-binding tail include enzyme immobilization to starch or recovery and purification of target proteins from crude extracts.

Adsorption↗