Self-Assembled Nanoparticles of Dextrin Substituted with Hexadecanethiol

The amphiphilic molecule dextrin-VA-SC16 (dexC16) was synthesized and studied in this work. DexC16 has a hydrophilic dextrin backbone with grafted acrylate groups (VA) substituted with hydrophobic 1-hexadecanethiol (C16). A versatile synthetic method was developed allowing control of the dextrin degree of substitution with the hydrophobic chains (DSC16, number of alkyl chains per 100 dextrin glucopyranoside residues). Materials with different DSC16 were prepared and characterized using 1H NMR. DexC16 self-assembles in water through association of the hydrophobic alkyl chains, originating nanoparticles. The nanoparticles properties were studied by dynamic light scattering (DLS), fluorescence spectroscopy, and atomic force microscopy (AFM).

Gas-chromatographic approach to probe the absence of molecular inclusion in enantioseparations by carbohydrates. Investigation of linear dextrins (“acyclodextrins”) as novel chiral stationary phases

Acetylated/silylated maltooligosaccharides with different degrees of oligomerization have been tested as chiral stationary phases for enantioselective gas chromatography. The acyclic dextrin derivatives carrying tert-butyldimethylsilyl groups at the primary hydroxyl sites and acetyl groups at the secondary hydroxyl sites showed an unexpected ability for the enantioseparation of alpha-amino acid derivatives and halogenated compounds, in addition to some underivatized chiral compounds. Some examples of an improved enantioselectivity invoked by the linear CSPs as compared to that of cyclic oligosaccharides are demonstrated in this work. The results highlight the role of the polar external surface of the selector in lieu of the well-established inclusion mechanism of enantiorecognition by cyclic dextrins. Thus, the enantioseparation of chiral compounds on linear dextrin derivatives--devoid of a molecular cavity--sheds a new light on the mechanisms of enantiorecognition by cyclodextrin derivatives. In contrast to cyclodextrins, linear dextrins are readily accessible in both enantiomeric forms.

Fate and effect of quaternary ammonium compounds on a mixed methanogenic culture

The potential inhibitory effect of four quaternary ammonium compounds (QACs) and Vigilquat, a commercial sanitizer which is a mixture of the four QACs, was investigated at concentrations up to 100 mg/L using a mixed, mesophilic (35 degrees C) methanogenic culture. Dextrin and peptone were used as the carbon and energy sources. A batch assay conducted at a range of QAC concentrations showed that QACs were inhibitory to methanogens at and above 25 mg/L. Methanogenesis was more susceptible to QAC inhibition than acidogenesis. Adsorption of QACs on biomass was successfully simulated with the Freundlich isotherm equation. The inhibitory effect of Vigilquat on the mixed methanogenic culture was also investigated in a batch reactor fed with dextrin and peptone. Methanogens were inhibited when the total QAC concentration reached 30 mg/L and volatile fatty acids (VFAs) accumulated. However, methane production recovered in 57 days of incubation, and all VFAs were consumed, suggesting that a prolonged incubation period is necessary for the methanogens to overcome the transient inhibition at a relatively low QAC concentration. None of the QACs tested in this study was biodegraded under methanogenic conditions.

Novel hydrogel obtained by chitosan and dextrin-VA co-polymerization

A novel hydrogel was obtained by reticulation of chitosan with dextrin enzymatically linked to vinyl acrylate (dextrin-VA), without cross-linking agents. The hydrogel had a solid-like behaviour with G' (storage modulus) >> G'' (loss modulus). Glucose diffusion coefficients of 3.9 x 10(-6) +/- 1.3 x 10(-6) cm(2)/s and 2.9 x 10(-6) +/- 0.5 x 10(-6) cm(2)/s were obtained for different substitution degrees of the dextrin-VA (20% and 70% respectively). SEM observation revealed a porous structure, with pores ranging from 50 microm to 150 microm.

[Immobilized glucoamylase: A biocatalyst of dextrin hydrolysis]

Heterogeneous biocatalysts of starch conversion based on glucoamylase and carbon-containing carriers were obtained, and their biocatalytic properties in enzymatic hydrolysis of corn dextrins were studied. It was shown that the morphology of the surface carbon layer of carriers markedly affected the properties of biocatalysts. Glucoamylase that was immobilized by adsorption on the surface of carriers covered with a layer of catalytic fibrous or pyrolytic carbon had the maximum enzymatic activity and stability, whereas the biocatalysts prepared on the basis of carriers that had no carbon layer or were covered with graphite-like surface carbon had a low activity and stability.

Biosynthesis of radiolabeled cellodextrins by the Clostridium thermocellum cellobiose and cellodextrin phosphorylases for measurement of intracellular sugars

The Clostridium thermocellum cellobiose and cellodextrin phosphorylases (glucosyl transferases) in the cell extract were used to synthesize radiolabeled cellodextrins with a degree of polymerization (DP=2-6) from nonradioactive glucose-1-phosphate and radioactive glucose. Chain lengths of synthesized cellodextrin were controlled by the absence or presence of dithiothreitol and by reaction conditions. All cellodextrins have the sole radioactive glucose unit located at the reducing ends. Mixed cellodextrins (G2-G6) were separated efficiently by size-exclusion chromatography or less efficiently by thin-layer chromatography. A new rapid sampling device was developed using disposable syringes containing an ultracold methanol-quenching buffer. It was simple, less costly, and especially convenient for anaerobic fermentation. After an impulse feed of radiolabeled cellobiose, the intracellular sugar levels were measured after a series of operations-sampling, extracting, concentrating, separating, and reading. Results showed that the largest amount of radioactivity was cellobiose with lesser amounts of glucose, cellotriose, and cellotetraose, and an average DP of intracellular cellodextrins was ca. 2.

Starch biosynthesis: the primer nonreducing-end mechanism versus the nonprimer reducing-end two-site insertion mechanism

Two mechanisms are recognized for polysaccharide chain elongation: (a) the nonreducing-end, primer-dependent mechanism and (b) the reducing-end, two-site insertion mechanism. We recently demonstrated the latter mechanism for starch biosynthesis by pulsing starch granules with ADP-[14C]Glc and chasing with ADPGlc for eight varieties of starch granules. Others have reported the addition of glucose from ADPGlc to the nonreducing ends of maltose, maltotriose, and maltopentaose and a branched maltopentasaccharide. It was concluded that starch chains are biosynthesized by the addition of glucose to the nonreducing ends of maltodextrin primers. In this study, we reinvestigated the maltodextrin reactions by reacting three kinds of starch granules from maize, wheat, and rice with ADP-[14C]Glc in the absence and presence of maltose (G2), maltotriose (G3), and maltodextrin (d.p.12) and found that they inhibited starch biosynthesis rather than stimulating it, as would be expected for primers. The major product in the presence of G2 was G3 with decreasing amounts of G4-G9 and the major products in the presence of G3 was G4 and G5, with decreasing amounts of G6-G9. It was concluded that maltodextrins are acceptors rather than primers. This was confirmed by pulsing the starch granules with ADP-[14C]Glc and chasing with G2, G3, and G6, which gave release of 14C-label from the pulsed granules in the absence of ADPGlc, further demonstrating that maltodextrins are acceptors that inhibit starch biosynthesis by releasing glucose from starch synthase, rather than acting as primers and stimulating biosynthesis.

Oligosaccharide synthesis in Fibrobacter succinogenes S85 and its modulation by the substrate

In this article we compared the metabolism of phosphorylated and unphosphorylated oligosaccharides (cellodextrins and maltodextrins) in Fibrobacter succinogenes S85 resting cells incubated with the following substrates: glucose; cellobiose; a mixture of glucose and cellobiose; and cellulose. Intracellular and extracellular media were analysed by (1)H-NMR and by TLC. The first important finding is that no cellodextrins were found to accumulate in the extracellular media of cells, regardless of the substrate; this contrasts to what is generally reported in the literature. The second finding of this work is that maltodextrins of degree of polymerization > 2 are synthesized regardless of the substrate, and can be used by the bacteria. Maltotriose plays a key role in this metabolism of maltodextrin. Maltodextrin-1-phosphate was detected in all the incubations, and a new metabolite, corresponding to a phosphorylated glucose derivative, was produced in the extracellular medium when cells were incubated with cellulose. The accumulation of these phosphorylated sugars increased with the degree of polymerization of the substrate.

Starch–dextrin mixtures as base excipients for extrusion–spheronization pellets

Extrusion-spheronization pellets are generally produced with microcrystalline cellulose (MCC) as the principal excipient, giving rise to particles of very high quality. A number of alternative excipients have been proposed and evaluated, mostly other cellulose derivatives (e.g. different grades of Avicel), or mixtures of MCCs and other excipients. In the present study, we evaluated the possible use of starch+agglutinant mixtures as principal excipients for extrusion-spheronization pellets, with the aim of producing pellets with more suitable properties for certain types of release. We first characterized the different excipients in terms of morphometry and basic physical properties. Subsequently, torque-rheometry was used to characterize the rheology of wetted masses of the different excipients and excipient mixtures, with the aim of determining optimal amount of wetting agent (water). We also evaluated the water absorption and water retention capacities of each excipient. In view of the results obtained, we produced pellets with the different starch+agglutinant mixtures (but without drug), and used image analysis to characterize pellet morphology. Our results show that some of the mixtures-notably starch (corn starch or wheat starch)+20% white dextrin-gave high-quality pellets with good size and shape distributions. In addition, the properties of the different materials tested suggest that it may be possible to obtain pellets with very different properties.

ATR-FT/IR study on the interactions between gliadins and dextrin and their effects on protein secondary structure

The effects of heat treatment and dextrin addition on the secondary structure of gliadins were investigated by means of attenuated total reflection Fourier transform infrared spectroscopy (ATR-FT/IR). Gliadins and gliadin/dextrin mixtures (before and after thermal treatment) were prepared as a dried protein film on the ATR-FT/IR zinc selenide cell plate and equilibrated at a water activity (a(w)) of 0.06. The results show that gliadins undergo conformational changes upon thermal treatment both in the absence and in the presence of dextrin. In particular, in the thermally treated gliadins, the decrease of the band at around 1651 cm(-)(1) and the increase of the bands at around 1628 and 1690 cm(-)(1) suggest a loss of alpha-helix structure and a higher content of protein aggregates. The same trend was observed in the presence of dextrin. Concerning the interactions between gliadins and dextrin, gliadin/dextrin mixtures show variations in the amide I region compared to native gliadins (e.g., an increase of the band at 1645 cm(-)(1) and the absence of the band at around 1668 cm(-)(1)) that might be due to hydrogen bond formation between gliadins and dextrin. It was also found that the spectrum of gliadin/dextrin mixtures was less affected by the hydration state than that of native gliadins, as observed from the differential spectra obtained by subtraction of the spectrum obtained at a(w) = 0.06 (driest condition tested) from the spectrum of the sample equilibrated at a(w) = 0.84. This could be due to the fact that C=O and N-H groups of gliadins are engaged to form hydrogen bonds with the hydroxyl groups of dextrin, and so they are not perturbed by the presence of water molecules. Finally, water activity effects on the secondary structure of gliadins are also discussed.

Cellodextrin preparation by mixed-acid hydrolysis and chromatographic separation

A procedure for preparation of purified cellodextrins in gram quantities was developed for use in biochemical and microbiological studies. Cellodextrins were prepared by hydrolyzing microcrystalline cellulose (Avicel) over a period of 4 to 5.5h in the presence of a mixture of 80% (v/v) concentrated hydrochloric acid ( approximately 37 wt.%) and 20% (v/v) concentrated sulfuric acid ( approximately 98 wt.%) at room temperature (22 degrees C). Acetone precipitation, washing ion exchange, and neutralization with barium hydroxide were used to generate a solution of mixed cellodextrins substantially free of acids and salts. Yields following hydrolysis and precipitation were approximately 0.05, approximately 0.07, approximately 0.06, and approximately 0.02 g/g cellulose for cellotriose (G(3)), cellotetraose (G(4)), cellopentose (G(5)), and cellohexose (G(6)), respectively. Cellodextrins with degrees of polymerization from 3 to 11 were separated chromatographically using a 29 x 5-cm I.D. Bio-Rad AG50W-X4 column arranged in series with a 91 x 5-cm I.D. Bio-Gel P4 column. This two-column system was used to obtain cellodextrin preparations at 240 mg/day for G(3), 330 mg/day for G(4), 260 mg/day for G(5), and 130 mg/day for G(6), with purity >99% for G(3), G(4), and G(5) and >95% for G(6). The overall procedure achieves yields comparable to the highest previously reported, employs a separation system that can readily be reused for multiple runs, and avoids use of fuming HCl.

Physicochemical characterization of solid dispersions of indomethacin with PEG 6000, Myrj 52, lactose, sorbitol, dextrin, and Eudragit E100

The purpose of this study was to prepare and characterize solid dispersions of indomethacin with polyethylene glycol (PEG) 6000, Myrj 52, Eudragit E100, and different carbohydrates such as lactose, mannitol, sorbitol, and dextrin. Indomethacin is a class II substance according to the Biopharmaceutics Classification System. It is a poorly water soluble antirheumatic agent. The goal was to investigate whether the solid dispersion can improve the dissolution properties of indomethacin. The solid dispersions were prepared by three different methods depending on the type of carrier. The evaluation of the properties of the dispersions was performed using solubility measurements, dissolution studies, Fourier-transform infrared spectroscopy, and x-ray powder diffractometery. The results indicate that lactose, mannitol, sorbitol, and especially Myrj 52 are suitable carriers to enhance the in vitro dissolution rate of indomethacin at pH 7.2. Eudragit E100, Myrj 52, and mannitol increase the dissolution properties at pH 1.2. The data from the x-ray diffraction showed that the drug was still detectable in its solid state in all solid dispersions except solid dispersions with dextrin and high amounts of mannitol. However, the results from infrared spectroscopy together with those from x-ray diffraction showed well-defined drug-carrier interactions for dextrin coevaporates.

Acid hydrolysis of native and annealed starches and branch-structure of their Naegeli dextrins

Eight commercial starches, including common corn, waxy corn, wheat, tapioca, potato, Hylon V, Hylon VII, and mung bean starch, were annealed by a multiple-step process, and their gelatinization characteristics were determined. Annealed starches had higher gelatinization temperatures, reduced gelatinization ranges, and increased gelatinization enthalpies than their native starches. The annealed starches with the highest gelatinization enthalpies were subjected to acid hydrolysis with 15.3% H2SO4, and Naegeli dextrins were prepared after 10 days' hydrolysis. Annealing increased the acid susceptibility of native starches in the first (rapid) and the second (slow) phases with potato starch showing the greatest and high amylose starches showing the least changes. Starches with a larger shift in onset gelatinization temperature also displayed a greater percent hydrolysis. The increase in susceptibility to acid hydrolysis was proposed to result from defective and porous structures that resulted after annealing. Although annealing perfected the crystalline structure, it also produced void space, which led to porous structures and possible starch granule defects. The molecular size distribution and chain length distribution of Naegeli dextrins of annealed and native starches were analyzed. The reorganization of the starch molecule during annealing occurred mainly within the crystalline lamellae. Imperfect double helices in the crystalline lamellae improved after annealing, and the branch linkages at the imperfect double helices became protected by the improved crystalline structure. Therefore, more long chains were observed in the Naegeli dextrins of annealed starches than in native starches.

Starch biosynthesis: sucrose as a substrate for the synthesis of a highly branched component found in 12 varieties of starches

D-[14C]glucose was incorporated into starch when 12 varieties of starch granules were incubated with [14C]sucrose. Digestion of the 14C-labeled starches with porcine pancreatic alpha amylase showed that a high percentage (16.1-84.1%) of the synthesized starch gave a relatively high molecular weight alpha-limit dextrin. Hydrolysis of the 12 varieties of starch granules by alpha amylase, without sucrose treatment, also gave an alpha-limit dextrin, ranging in amounts from 0.51% (w/w) for amylomaize-7 starch to 8.47% (w/w) for rice starch. These alpha-limit dextrins had relatively high molecular weights, 2.47 kDa for amylomaize-7 starch to 5.75 kDa for waxy maize starch, and a high degree of alpha-(1-->6) branching, ranging from 15.6% for rice starch to 41.1% for shoti starch. ADPGlc and UDPGlc did not synthesize a significant amount (1-2%) of the branched component, suggesting that sucrose is the probable substrate for the in vivo synthesis of the component and that sucrose is not first converted into a nucleotide-glucose diphosphate intermediate.

Complexation trends and binding constants between dextrin oligomers and small molecules as measured through affinity capillary electrophoresis

Quantitative aspects of a previously reported pre-equilibration affinity/capillary electrophoretic methodology (Hong, M., et al., Anal. Chem. 1998, 70, 3590-3597) were studied using fluorescently labeled oligosaccharides and analgesic drugs. Frontal analysis capillary electrophoresis (FA-CE) was investigated for these interaction systems. In order to fulfill certain FA requirements, the analysis conditions of the sugar-drug combinations had to be adjusted individually. Only after the establishment of these conditions, acceptable binding data (association constants) could be obtained. The constants are in the range of weak hydrogen bonding and are comparable to the constants that were independently obtained through 1H nuclear magnetic resonance (NMR) spectroscopy.

Preparation of indigestible pyrodextrins from different starch sources

Starch-modifying processes, such as pyrodextrinization, are potential ways to alter the nutritional features of this polysaccharide. A widely used method for pyrodextrinizing maize starch was also applied to lentil, sorghum, cocoyam, sagu, and cassava starches, and the in vitro digestibility of the products was evaluated. Pyrodextrins were produced by heating starch at 140 degrees C for 3 h, with catalytic amounts of HCl. The enzymatically available starch content of all preparations decreased by 55-65% after modification. Thus, pyrodextrinization seems to be an effective way to produce indigestible glucans from different starches. Pyrodextrins obtained were complex mixtures of starch derivatives with a wide range of molecular weight as estimated by gel filtration chromatography. Both their molecular weight profiles and contents of indigestible fractions varied with starch source. Experiments with lentil and cassava starches showed that changing dextrinization conditions also affects the susceptibility to enzymatic hydrolysis of the product.

Phosphorylation of starch and dextrin by dry-heating in the presence of phosphate, and their calcium phosphate-solubilizing ability

Starch and dextrin were phosphorylated by dry-heating in the presence of phosphate, and their properties were examined. The phosphorylation of starch was accelerated with decreasing moisture, rising incubation temperature and prolongation of the incubation period. However, a rise in incubation temperature, and lengthened incubation period caused increased browning and degradation. A decrease in the pH from 5.5 to 3.0 resulted in a modest increase of phosphorylation, but also marked browning and degradation. When potato starch was phosphorylated at 140 degrees C and pH 5.5 for 24 h, its phosphorus content was increased up to 3.47%, with fewer side reactions. Phosphorlylated starch and dextrin had calcium phosphate-solubilizing abitity. Phosphorylated dextrin with 2.42% phosphorus had about half the calcium phosphate-solubilizing ability of casein phosphopeptide (CPP). The possibility of substituting of phosphorylated starch and dextrin for CPP as a calcium phosphate-absorption enhancing material is discussed herein.

Dextrin characterization by high-performance anion-exchange chromatography--pulsed amperometric detection and size-exclusion chromatography--multi-angle light scattering--refractive index detection

Starch hydrolysis products, or dextrins, are widely used throughout the food industry for their functional properties. Dextrins are saccharide polymers linked primarily by alpha-(1 --> 4) D-glucose units and are prepared by partial hydrolysis of starch. Hydrolysis can be accomplished by the use of acid, enzymes, or by a combination of both. The hydrolysis products are typically characterized by the "dextrose equivalent" (DE), which refers to the total reducing power of all sugars present relative to glucose. While the DE gives the supplier and buyer a rough guide to the bulk properties of the material, the physiochemical properties of dextrins are dependent on the overall oligosaccharide profile. High-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection and size-exclusion chromatography (SEC) with multi-angle light-scattering and refractive index detection were used to characterize dextrins from commercial sources. HPAEC was used to acquire the oligosaccharide profile, and SEC to obtain an overall molar mass distribution. These methods in combination extended our understanding of the relationship between oligosaccharide profile, DE, and the hydrolysis process. Data from the two techniques enabled a method for estimating the DE that gave results in reasonable agreement with the accepted titration method.

Fractionation of starch hydrolysates into dextrins with narrow molecular mass distribution and their detection by high-performance anion-exchange chromatography with pulsed amperometric detection

Low levels of high-molecular-mass dextrins in starch hydrolysates can be detected by high-performance anion-exchange chromatography with pulsed amperometric detection in spite of their low responses by dialysis of the starch hydrolysate and fractionation of the resulting adialysate with ethanol (final concentration 30-80% at 6 degrees C). In doing so, dextrin fractions with a relatively narrow molecular mass distribution were obtained.

Activity and Survival of Spray-Dried Beijerinckia sp. Microencapsulated in Different Carbohydrates

This study examined the possibility of preserving Beijerinckia cultures by encapsulation using a spray drier, for use in biotechnological processes in the production of biopolymers. An adequate choice of the wall (coating) material is one of the factors that will determine the degree of cell survival and the maintenance of fermentative activity in the encapsulated inoculum. Malt dextrin, dehydrated glucose syrups, modified starch, and acacia (gum arabic) were used as wall materials. The results showed that spray-dried Beijerinckia encapsulated in malt dextrin, stored for 2 mo, and inoculated into sterile must after rehydration presented the greatest stability with respect to fermentative activity, although the glucose-encapsulated cells showed the highest percentage of viability during spray drying and during the storage period.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of dextran and dextrin derivatives

Application of matrix-assisted laser desorption/ionization (MALDI) to the analysis of dextran and dextrin derivatives, specifically glucose saccharides, by time-of-flight (TOF) mass spectrometry has been reported. MALDI-TOF analysis was carried out on alpha-, beta- and gamma-cyclodextrin, two O-methylated-beta-cyclodextrins of differing degrees of substitution (DS) and dextrans (a linear glucose saccharide), as pure and doped solutions and as mixtures of two or more of these. Doping was carried out with trace amounts of inorganic salts. The purpose of the analysis of the cyclodextrins was to determine whether they would form inclusion complexes with the various cations added, or whether less specific cation addition/exchange was occurring either prior to desorption or in the gas phase.

Simultaneous separation of different enantiomeric pairs in capillary electrophoresis by mixing different hemispherodextrins, a very versatile class of receptors

Six different racemates of the profen family were used as analytes in order to test the chiral selector properties of three members of a new class of cyclodextrin derivatives, hemispherodextrins (HMs), in capillary electrophoresis. In addition to experiments carried out to separate each enantiomeric pair one by one, other experiments were carried out on samples containing all six enantiomeric pairs. Electropherograms were obtained either by adding a single HM to the background electrolyte (BGE), or a binary mixture of HMs. The results obtained confirm the excellent chiral selector properties of the HMs, and furthermore show that these compounds can also be used for achiral selection. When mixing different HMs, a complementary effect in chiral selectivity is observed, which, in our opinion, deserves further study.

Chemoenzymatic syntheses of linear and branched hemithiomaltodextrins as potential inhibitors for starch-debranching enzymes

Oligosaccharides embodying the S-maltosyl-6-thiomaltosyl structure have been readily synthesised by using convergent chemoenzymatic approaches. The key steps for the preparation of these molecules involved: 1) transglycosylation reactions of maltosyl fluorides onto suitable acceptors catalysed by the bacterial transglycosylase, cyclodextrin glycosyltransferase (CGTase), and 2) the SN2-type displacement of a 6-halide from acetylated acceptors by activated 1-thioglycoses. The target molecules, which were obtained in good overall yields, proved to be useful for investigating substrate binding in the active sites of several enzymes that act upon the alpha-1,6-linkage of pullulan and/or amylopectin. The compounds exhibit Ki values in the 2.5-1350 microM range with the different enzymes, and the highest affinity found by using these molecules was seen for the pullulanase from Bacillus acidopullulyticus. Both barley-malt limit dextrinase and pullulanase type II from Thermococcus hydrothermalis only recognised the longest linear thiooligosaccharide, while a branched heptasaccharide was the strongest inhibitor of pullulanase from Klebsiella planticola.

Cyclomaltodextrinase, neopullulanase, and maltogenic amylase are nearly indistinguishable from each other

Over 20 enzymes denoted as cyclomaltodextrinase, maltogenic amylase, or neopullulanase that share 40-86% sequence identity with each other are found in public data bases. These enzymes are distinguished from typical alpha-amylases by containing a novel N-terminal domain and exhibiting preferential substrate specificities for cyclomaltodextrins (CDs) over starch. In this research field, a great deal of confusion exists regarding the features distinguishing the three groups of enzymes from one another. Although a different enzyme code has been assigned to each of the three different enzyme names, even a single differentiating enzymatic property has not been documented in the literature. On the other hand, an outstanding question related to this issue concerns the structural basis for the preference of these enzymes for CDs. To clarify the confusion and to address this question, we have determined the structures of two enzymes, one from alkalophilic Bacillus sp. I-5 and named cyclomaltodextrinase and the other from a Thermus species and named maltogenic amylase. The structure of the Bacillus enzyme reveals a dodecameric assembly composed of six copies of the dimer, which is the structural and functional unit of the Thermus enzyme and an enzyme named neopullulanase. The structure of the Thermus enzyme in complex with beta-CD led to the conclusion that Trp47, a well conserved N-terminal domain residue, contributes greatly to the preference for beta-CD. The common dimer formation through the novel N-terminal domain, which contributes to the preference for CDs by lining the active-site cavity, convincingly indicates that the three groups of enzymes are not different enough to preserve the different names and enzyme codes.