Publications by authors named "Atsuo Kimura"

The glucoconjugation between linear chimeric α-(1→4)- and α-(1→6)-glucosidic segments exhibits functional properties throughout their structure. In this study, we enzymatically synthesized three new series of chimeric nonreducing isomaltomegalosaccharides (N-IMS-n/m), each featuring a constant n, α-(1→4)-segment (average degree of polymerization, DP = 22-25) at the nonreducing terminal, and varying m, α-(1→6)-main chain lengths (DP = 7-53). The synthesized compounds-N-IMS-25/7, N-IMS-24/19, and N-IMS-22/53-were compared to amylose (DP = 28) and previous samples of N-IMS-15/35 and D-IMS-28.

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Ruminant animals rely on the activities of -glucosidases from residential microbes to convert feed fibers into glucose for further metabolic uses. In this report, we determined the structures of Br2, which is a glycoside hydrolase family 1 -glucosidase from the bovine rumen metagenome. Br2 folds into a classical (/)-TIM barrel domain but displays unique structural features at loop 5→5 and -helix 5, resulting in different positive subsites from those of other GH1 enzymes.

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Article Synopsis
  • Isomaltomegalosaccharides (IMS) can effectively solubilize water-insoluble compounds by utilizing their α-(1→4) and α-(1→6)-segments, which help in forming and stabilizing complexes with these compounds.
  • Previous attempts at synthesizing IMS with a single α-(1→4)-segment resulted in short chain lengths that were not effective for strong encapsulation, leading researchers to explore longer segments.
  • This study successfully created D-IMS, which has two α-(1→4)-segments, through a specific enzymatic process; the modified compound demonstrated improved water solubility and could encapsulate various bioactive substances like aromatic drugs and flavonoids.
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β-Xylosidases catalyze the hydrolysis of xylooligosaccharides to xylose in the final step of hemicellulose degradation. AnBX, which is a GH3 β-xylosidase from Aspergillus niger, has a high catalytic efficiency toward xyloside substrates. In this study, we report the three-dimensional structure and the identification of catalytic and substrate binding residues of AnBX by performing site-directed mutagenesis, kinetic analysis, and NMR spectroscopy-associated analysis of the azide rescue reaction.

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Polysaccharides of tamarind seed, a byproduct of the tamarind pulp industry, displayed a potential solubility improvement of lipophilic bioactive molecules but their textural characteristics hinder the dietary formulation. In contrast, the commonly available xyloglucan oligosaccharides (XOSs) with degrees of polymerization (DPs) of 7, 8, and 9 were too short to maintain their ability. The binding capacity of the between sizes is unknown due to a lack of appropriate preparation.

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Lipophilic azo dyes are practically water-insoluble, and their dissolution by organic solvents and surfactants is harmful to biological treatment with living cells and enzymes. This study aimed to evaluate the feasibility of a newly synthesized nonreducing terminal chimeric isomaltomegalosaccharide (N-IMS) as a nontoxic solubilizer of four simulated lipophilic azo dye wastes for enzymatic degradation. N-IMS bearing a helical α-(1 → 4)-glucosidic segment derived from a donor substrate α-cyclodextrin was produced by a coupling reaction of cyclodextrin glucanotransferase.

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Glucose, a common monosaccharide in nature, is dominated by the d-enantiomer. Meanwhile, the discovery of l-glucose-utilizing bacteria and the elucidation of their metabolic pathways 10 years ago suggests that l-glucose exists naturally. Most carbohydrates exist as glycosides rather than monosaccharides; therefore, we expected that nature also contains l-glucosides.

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Isomaltomegalosaccharide (IMS) is a long chimeric glucosaccharide composed of α-(1 → 6)- and α-(1 → 4)-linked segments at nonreducing and reducing ends, respectively; the hydrophilicity and hydrophobicity of these segments are expected to lead to bifunctionality. We enzymatically synthesized IMS with average degrees of polymerization (DPs) of 15.8, 19.

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The glycoside hydrolase family 17 β-1,3-glucanase of (VvGH17) has two unknown regions in the N- and C-termini. Here, we characterized these domains by preparing mutant enzymes. VvGH17 demonstrated hydrolytic activity of β-(1→3)-glucan, mainly producing laminaribiose, but not of β-(1→3)/β-(1→4)-glucan.

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Dextran dextrinase (DDase) catalyzes formation of the polysaccharide dextran from maltodextrin. During the synthesis of dextran, DDase also generates the beneficial material isomaltomegalosaccharide (IMS). The term megalosaccharide is used for a saccharide having DP = 10-100 or 10-200 (DP, degree of polymerization).

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Glycoside hydrolase family 15 (GH15) inverting enzymes contain two glutamate residues functioning as a general acid catalyst and a general base catalyst, for isomaltose glucohydrolase (IGHase), Glu178 and Glu335, respectively. Generally, a two-catalytic residue-mediated reaction exhibits a typical bell-shaped pH-activity curve. However, IGHase is found to display atypical non-bell-shaped pH-k and pH-k /K profiles, theoretically better-fitted to a three-catalytic residue-associated pH-activity curve.

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Glycoside hydrolase family 68 (GH68) enzymes catalyze β-fructosyltransfer from sucrose to another sucrose, the so-called transfructosylation. Although regioselectivity of transfructosylation is divergent in GH68 enzymes, there is insufficient information available on the structural factor(s) involved in the selectivity. Here, we found two GH68 enzymes, β-fructofuranosidase (FFZm) and levansucrase (LSZm), encoded tandemly in the genome of Zymomonas mobilis, displayed different selectivity: FFZm catalyzed the β-(2→1)-transfructosylation (1-TF), whereas LSZm did both of 1-TF and β-(2→6)-transfructosylation (6-TF).

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Purpose: Thoracoscopic bullectomy is a common treatment modality for spontaneous pneumothorax but can result in a high frequency of postoperative recurrent pneumothorax in young patients. This retrospective study compared the recurrence rate of pneumothorax following conventional thoracoscopic bullectomy to that following bullectomy using a low-density polyglycolic acid mesh to cover the staple line.

Methods: Group A comprised 237 patients who experienced 294 episodes of pneumothorax and underwent thoracoscopic bullectomy alone, and Group B comprised 130 patients who experienced 155 episodes of pneumothorax and underwent bullectomy with polyglycolic acid mesh used to cover the visceral pleura.

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Paenibacillus sp. 598K produces cycloisomaltooligosaccharides (CIs) in culture from dextran and starch. CIs are cyclic oligosaccharides consisting of seven or more α-(1 → 6)-linked-D-glucose residues.

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α-Glucosidase from Aspergillus niger (AgdA; typical α-1,4-glucosidase) is known to industrially produce α-(1→6)-glucooligosaccharides. This fungus also has another α-glucosidase-like protein, AgdB. To learn its function, wild-type AgdB was expressed in Pichia pastoris.

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Makgeolli is a traditional Korean alcoholic rice beverage. It is brewed of ingredients containing starch, Nuruk, and water. In order to improve the quality and functionality of Makgeolli, the fermented buckwheat containing 18.

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Herein, we investigated enzymatic properties and reaction specificities of Streptococcus mutans dextranase, which hydrolyzes α-(1→6)-glucosidic linkages in dextran to produce isomaltooligosaccharides. Reaction specificities of wild-type dextranase and its mutant derivatives were examined using dextran and a series of enzymatically prepared p-nitrophenyl α-isomaltooligosaccharides. In experiments with 4-mg·mL dextran, isomaltooligosaccharides with degrees of polymerization (DP) of 3 and 4 were present at the beginning of the reaction, and glucose and isomaltose were produced by the end of the reaction.

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Megalo-type isomaltosaccharides are an enzymatically synthesized foodstuff produced by transglucosylation from maltodextrin, and they contain a mid-chain length polymer of D-glucose with α-1,6-glycoside linkages. The injection of a solution of megalo-type isomaltosaccharides (1-4%(w/v), average DP = 12.6), but not oligo-type isomaltosaccharides (average DP = 3.

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Glycoside hydrolase family 97 (GH97) is one of the most interesting glycosidase families, which contains inverting and retaining glycosidases. Currently, only two enzyme types, α-glucoside hydrolase and α-galactosidase, are registered in the carbohydrate active enzyme database as GH97 function-known proteins. To explore new specificities, BT3661 and BT3664, which have distinct amino acid sequences when compared with that of GH97 α-glucoside hydrolase and α-galactosidase, were characterized in this study.

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sp. 598K α-1,6-glucosyltransferase (Ps6TG31A), a member of glycoside hydrolase family 31, catalyzes exo-α-glucohydrolysis and transglucosylation and produces α-1,6-glucosyl-α-glucosaccharides from α-glucan via its disproportionation activity. The crystal structure of Ps6TG31A was determined by an anomalous dispersion method using a terbium derivative.

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Aspergillus niger α-glucosidase (ANG), a member of glycoside hydrolase family 31, catalyzes hydrolysis of α-glucosidic linkages at the non-reducing end. In the presence of high concentrations of maltose, the enzyme also catalyzes the formation of α-(1→6)-glucosyl products by transglucosylation and it is used for production of the industrially useful panose and isomaltooligosaccharides. The initial transglucosylation by wild-type ANG in the presence of 100 mM maltose [Glc(α1-4)Glc] yields both α-(1→6)- and α-(1→4)-glucosidic linkages, the latter constituting ~25% of the total transfer reaction product.

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The recombinant catalytic α-subunit of N-glycan processing glucosidase II from Schizosaccharomyces pombe (SpGIIα) was produced in Escherichia coli. The recombinant SpGIIα exhibited quite low stability, with a reduction in activity to <40% after 2-days preservation at 4 °C, but the presence of 10% (v/v) glycerol prevented this loss of activity. SpGIIα, a member of the glycoside hydrolase family 31 (GH31), displayed the typical substrate specificity of GH31 α-glucosidases.

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Paenibacillus sp. 598K produces cycloisomaltooligosaccharides (cyclodextrans) from starch even in the absence of dextran. Cycloisomaltooligosaccharide glucanotransferase synthesizes cycloisomaltooligosaccharides exclusively from an α-(1 → 6)-consecutive glucose chain consisting of at least four molecules.

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Unlabelled: The preparation of a glycosynthase, a catalytic nucleophile mutant of a glycosidase, is a well-established strategy for the effective synthesis of glycosidic linkages. However, glycosynthases derived from α-glycosidases can give poor yields of desired products because they require generally unstable β-glycosyl fluoride donors. Here, we investigate a transglycosylation catalyzed by a catalytic nucleophile mutant derived from a glycoside hydrolase family (GH) 97 α-galactosidase, using more stable β-galactosyl azide and α-galactosyl fluoride donors.

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Streptomyces thermolilacinus mannanase (StMan), which requires Ca(2+) for its enhanced thermal stability and hydrolysis activity, possesses two Ca(2+) -binding sites in loop6 and loop7. We evaluated the function of the Ca(2+) -binding site in loop7 and the hydrogen bond between residues Ser247 in loop6 and Asp279 in loop7. The Ca(2+) -binding in loop7 was involved only in thermal stability.

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