Journal of applied glycoscience最新文献

The application of flour is determined by the composition of its starch and storage proteins. Previously isolated diploid waxy wheat is known to be amylose-free and possesses the same amylopectin structure as the wild-type. To reveal its characteristics, starch, protein, lipid, fiber, gluten, and allergen contents and rheological properties were analyzed and compared to its parental wild-type diploid wheat and commercially available hexaploid wheats. The results showed that the starch content of diploid waxy wheat was similar, but its protein, lipid, and fiber contents were higher than that of the wild-type. In addition, diploid waxy wheat produced high levels of gluten unlike its wild-type while its allergen level was similar to its wild-type. The storage modulus of diploid waxy wheat was significantly lower than that of other wheat lines at high temperatures. These results suggest that diploid waxy wheat holds different characteristics from hexaploid wheats for food processing.

The branched structure of amylose was probed using concanavalin A (ConA) lectin, which forms precipitable aggregates with highly branched glucans, such as glycogen and amylopectin. Rice (japonica cultivar) amylose was fractionated from de-fatted, gelatinized starch by precipitation with 1-butanol (BuOH) and purified by ultracentrifugation and repeated crystallization. The purified amylose still has short side chains, whose chain-length (CL) distribution resembles that of amylopectin. More than 96 wt% of the amylose was not precipitated with ConA and remained in the resultant supernatant. The amylose recovered from the supernatant exhibited essentially the same size distributions of molecules and the CL distributions of main and side chains as those of amylose without ConA precipitation. The molar % of branched molecules was slightly decreased by ConA precipitation (-ConA, 11.6; +ConA, 8.1). These results suggest that the side chains detected in BuOH-precipitable amylose preparation are essentially attributable to amylose itself. Also, the non-precipitable nature of the branched molecules of amylose by ConA supports our previous proposal that the organization of the short side chains on amylose molecules is quite different from that found in amylopectin, in which the short side chains are arranged in a cluster fashion, and the branched glucan interacts with ConA to form precipitable aggregates. A tiny amount of ConA-precipitable glucan was detected, but its CL distribution was inconsistent with the size distribution of the branched molecules. Even if the precipitable glucans were fragments of amylopectin, their contribution to the branches detected in amylose should be minor.

D-Allulose (D-psicose) is a rare sugar and a C-3 epimer of D-fructose. D-Allulose has been reported to have several health benefits via its alteration of both glucose and lipid metabolism. It was previously reported that D-allulose alters the hepatic metabolomic profile. Although the kidneys are crucial organs in metabolic regulation, the effects of D-allulose on renal metabolism have not yet been established. Therefore, this study was designed to capture the overall metabolic response in the kidneys to D-allulose. This was done by providing an AIN-93G diet to Wistar rats, with or without 3 % D-allulose, for four weeks. Renal tissue and blood samples were collected after a 3-hour fasting for evaluation of the renal metabolic profile and their related plasma parameters. D-Allulose increased renal weight without changes in the plasma indices associated with reduced renal function. Metabolic profiling identified a total of 264 peaks. As the contribution rate was too low in the principal component analysis results of the metabolic profiling results, we evaluated the metabolites that were significantly different between two groups and identified 23 up-regulated and 26 down-regulated metabolites in the D-allulose group. D-Allulose also had significant influence on several metabolites involved in glucose metabolism, amino acid metabolism, and purine metabolism. Moreover, the levels of trimethylamine N-oxide and symmetric dimethylarginine, which are associated with several diseases such as chronic kidney disease and cardiovascular disease decreased following D-allulose diets. This study showed that D-allulose affects the renal metabolic profile, and our findings will help elucidate the function of D-allulose.

We recently found two α-L-glucosidases, which can hydrolyze p-nitrophenyl α-L-glucopyranoside (PNP L-Glc) rather than p-nitrophenyl α-L-fucopyranoside, in glycoside hydrolase family 29. This study evaluated their substrate specificity for p-nitrophenyl α-L-rhamnopyranoside (PNP L-Rha), α-L-quinovopyranoside (PNP L-Qui), and α-L-xylopyranoside (PNP L-Xyl), of which structure is similar to PNP L-Glc. The two α-L-glucosidases had little activity toward PNP L-Rha. They exhibited higher k _cat/K _m values for PNP L-Qui but smaller for PNP L-Xyl than for PNP L-Glc. The molecular docking studies indicated that these specificities were correlated well with the active-site structure of the α-L-glucosidases. The finding that α-L-quinovoside, which has been suggested to occur in nature, is also a substrate for α-L-glucosidases indicates that this enzyme are not solely dedicated to α-L-glucoside hydrolysis.

To overcome incompatibility issues and increase the possibility of blood transfusion, technologies that enable efficient conversion of A- and B-type red blood cells to the universal donor O-type is desirable. Although several blood type-converting enzymes have been identified, detailed understanding about their molecular functions is limited. α-Galactosidase from Bifidobacterium bifidum JCM 1254 (AgaBb), belonging to glycoside hydrolase (GH) 110 subfamily A, specifically acts on blood group B antigen. Here we present the crystal structure of AgaBb, including the catalytic GH110 domain and part of the C-terminal uncharacterized regions. Based on this structure, we deduced a possible binding mechanism of blood group B antigen to the active site. Site-directed mutagenesis confirmed that R270 and E380 recognize the fucose moiety in the B antigen. Thermal shift assay revealed that the C-terminal uncharacterized region significantly contributes to protein stability. This region is shared only among GH110 enzymes from B. bifidum and some Ruminococcus species. The elucidation of the molecular basis for the specific recognition of blood group B antigen is expected to lead to the practical application of blood group conversion enzymes in the future.

Transient absorption at 340 nm under alkaline conditions has long been used to detect the presence of 3-keto-O-glycosides without understanding the molecular basis of the absorbance. The time course of A_{340 nm} for the alkaline treatment of 3-ketolevoglucosan, an intramolecular 3-keto-O-glycoside, was investigated to identify the three products generated through alkaline treatment. By comparing the spectra of these compounds under neutral and alkaline conditions, we identified 1,5-anhydro-D-erythro-hex-1-en-3-ulose (2-hydroxy-3-keto-D-glucal) as being the compound responsible for the absorption.

The objective of this study was to characterize the endosperm starch in rice that ectopically overexpressed the α-amylase. Transgenic rice plants, transformed with cauliflower mosaic virus 35S promoter driven AmyI-1 (35S::AmyI-1) and AmyII-4 (35S::AmyII-4), and 10 kDa prolamin promoter driven AmyI-1 (P10::AmyI-1), were cultivated under standard conditions (23 °C, 12 h in the dark/ 26 °C, 12 h in the light), and brown grains were subsequently harvested. Each grain displayed characteristic chalkiness, while electron microanalyzer (EPMA)-SEM images disclosed numerous small pits on the surface of the starch granules, attributable to α-amylase activity. Fluorescence labeling and capillary electrophoresis analysis of starch chain length distribution revealed no significant alterations in the starches of 35S::AmyI-1 and 35S::AmyII-4 transgenic rice compared to the wild-type. Conversely, the extremely short α-glucan chains (DP 2-8) exhibited a dramatic increase in the P10::AmyI-1 starch. Rapid visco-analyzer analysis also identified variations in the chain length distribution of P10::AmyI-1 starch, manifesting as changes in viscosity. Moreover, ¹H-NMR analysis uncovered dynamic modifications in the molecular structure of starch in rice grain transformed with P10::AmyI-1, which was found to possess unprecedented structural characteristics.

Water-soluble carbohydrates commonly exist in an amorphous state in foods and undergo glass-rubber transition (glass transition) at the glass transition temperature (T_g). The critical water content (W_c) and critical water activity (a_wc) are the water content and water activity (a_w) at which the glass transition occurs at 298 K (typical ambient temperature), respectively. For amorphous water-soluble carbohydrates, W_c can be predicted from the T_g of anhydrous solid (T_gs) using previously reported equations. However, an approach for predicting a_wc is still lacking. This study aimed to establish an a_wc-predictive approach for amorphous water-soluble carbohydrates based on T_gs. First, the water sorption isotherms of four hydrogenated starch hydrolysates were investigated, and the results were analyzed using the Guggenheim-Anderson-de Boer (GAB) model. Second, the effect of T_gs on the GAB parameters (C, K, and W_m) was evaluated using the T_gs values reported in previous literatures. C and W_m decreased and increased logarithmically, respectively, with increasing 1/T_gs. K was fixed to 1 (constant), as it showed little variation. These results enabled the prediction of the GAB parameters from T_gs. The GAB model could then predict a_wc from W_c, which was determined using the previously established equations. The predicted a_wc values were in good agreement with the experimentally determined a_wc. Additionally, we demonstrated that this a_wc-prediction approach is also applicable to amorphous water-soluble electrolytes and partially water-insoluble carbohydrates. Thus, this approach can be used for the quality control of amorphous water-soluble carbohydrates and carbohydrate-based foods.

Trehalose is known to protect enzymes from denaturation. In the present study, we observed promotion of apple polyphenol oxidase (PPO) inactivation in a trehalose solution with thermal treatment. Crude PPO from Fuji apple was mixed with either sucrose or trehalose solutions, then the samples treated at 25 or 65 °C. In the presence of trehalose, PPO activities were markedly decreased upon treatment at 65 °C with increasing trehalose concentration. Furthermore, the reduction in PPO activity in the presence of trehalose was proportional to storage time after thermal treatment and thermal treatment time. Comparing PPO activities between treatment time 0 and 90 min at 65 °C, activities decreased 89 % for trehalose concentration of 0.2 M. These results indicates that trehalose acts not only as inhibitor but as promoter of inactivation of PPO. The Lineweaver-Burk plot indicated that trehalose acts on PPO as a non-competitive inhibitor during the 65 °C treatment. Two mechanisms of PPO inactivation in the presence of trehalose were suggested; one is the suppression of PPO activation cause by a thermal treatment, and another is the conformational change to inactivation form of PPO in conjunction with trehalose and a thermal treatment. Additionally, apple juice including 0.2 or 0.5 M trehalose with 65 °C treatment indicated slow browning than the juice with 0.2 or 0.5 M sucrose or without sugars. This result demonstrates that the preventing of browning with trehalose is a viable industrial food process.

α-Mannosidase (ALMAN) extracted from onion (Allium cepa) was purified by column chromatography such as hydrophobic and gel filtration. ALMAN is an acidic α-mannosidase that exhibits maximum activity against pNP-α-Man at pH 4.0-5.0 at 50°C. Amino acid sequence analysis of ALMAN was consistent with α-mannosidase deduced from Allium cepa transcriptome analysis. The gene alman was amplified by PCR using mRNA extracted from onions, and a full-length gene of 3,054 bp encoding a protein of 1,018 amino acid residues was revealed. ALMAN is classified as Glycoside Hydrolase Family (GH) 38 and showed homology with other plant-derived α-mannosidases such as tomato and hot pepper.