A glycosylglucose consisting of two D-glucopyranose units connected by an alpha-(1->6)-linkage.
Identification
alpha-D-glucopyranosyl-(1->6)-D-glucopyranose
(Glc)2
6-O-alpha-D-glucopyranosyl-D-glucopyranose
alpha-D-Glc-(1->6)-D-Glc
alpha-D-Glcp-(1->6)-D-Glcp
alpha-D-glucosyl-(1->6)-D-glucose
Brachiose
Hunterioside
Isomaltose
isomaltose
Species
mus musculus
NCBI:txid10090 19425150
arabidopsis thaliana
brassica napus
saccharomyces cerevisiae
daphnia pulex
homo sapiens
NCBI:txid9606 10.1038/nbt.2488
NCBI:txid9606 22308371
NCBI:txid9606 10649708
Europe PubMed Central results
Maltose and isomaltose in uremic plasma following icodextrin administration.
Author: Burke RA, Moberly JB, Patel H, Shockley TR, Martis L.
Abstract: The presence of mixed disaccharides (maltose and isomaltose) in plasma from uremic patients has been previously investigated using gel-permeation chromatography. However, this method is unable to separate maltose (linked alpha-1-4) from isomaltose (linked alpha-1-6). We describe an alternative method using high-performance anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD) for the direct determination of maltose and isomaltose in uremic plasma. We measured maltose and isomaltose using HPAE-PAD in 6 normal subjects and in 15 uremic patients before and after once-daily icodextrin administration for at least 4 weeks. Both maltose and isomaltose were below limits of detection (< 1.0 mg/L) in plasma from normal controls. Patients with end-stage renal disease treated by continuous ambulatory peritoneal dialysis had elevated levels of isomaltose (23.6 +/- 8.3 mg/L) but low levels of maltose (< 3.0 mg/L). Treatment with icodextrin resulted in elevated plasma levels of maltose (range: 500-1600 mg/L), while levels of isomaltose declined to 9.8 +/- 5.2 mg/L (P < 0.0001 vs. baseline levels). We conclude that isomaltose (not maltose) is the primary disaccharide isomer that is elevated in the plasma of uremic patients, whereas maltose is the primary disaccharide isomer that is elevated following icodextrin administration. Furthermore, icodextrin administration results in an apparent reduction of isomaltose. Additional investigation will be required to address the mechanism for the reduction of isomaltose in patients treated by icodextrin.
Isomaltose formed by alpha-glucosidases triggers amylase induction in Aspergillus nidulans.
Author: Kato N, Murakoshi Y, Kato M, Kobayashi T, Tsukagoshi N.
Abstract: Among various alpha-glucobioses examined, isomaltose was the most effective inducer for amylase synthesis in Aspergillus nidulans. Amylase induction by maltose was completely inhibited by addition of castanospermine or cycloheximide, while induction by isomaltose was not affected by the inhibitors, suggesting that amylase induction by maltose requires inducible alpha-glucosidases. Disruption of the alpha-glucosidase A gene ( agdA), the alpha-glucosidase B gene ( agdB), or both genes did not abolish maltose-dependent induction, although amylase production induced by maltose decreased about 2-fold in the agdA/ agdB double disruptant, compared with that in the agdB disruptant at all concentrations tested. Upon induction by isomaltose, amylase synthesis was enhanced considerably in the agdB and agdA/ agdB disruptants. Even at 3 nM, isomaltose induced amylase production in the double disruptant, supporting the suggestion that isomaltose is a physiological inducer for amylase. Therefore, maltose must be converted to isomaltose by alpha-glucosidases prior to triggering amylase synthesis, but no specific alpha-glucosidase is required for amylase induction by maltose. Probably any alpha-glucosidases having isomaltose-forming activity, including AgdA and AgdB, may participate in amylase induction by maltose.
Identification and quantification of the plasma volume expander dextran in human urine by liquid chromatography-tandem mass spectrometry of enzymatically derived isomaltose.
Author: Guddat S, Thevis M, Schänzer W.
Abstract: Plasma volume expanders are used in sports in order to control haematological parameters and/or to mask erythropoietin (EPO) misuse. A reliable method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for doping control purposes, enabling the identification and quantification of the plasma volume expander dextran in human urine. The dextran polymer was enzymatically hydrolysed by alpha-1,6-glucosidase (dextranase) followed by acetylation of the generated isomaltose subunits, allowing the chromatographic separation of different disaccharides, such as lactose, saccharose and isomaltose, as well as the identification and quantification of the analyte in human urine. The method was used to determine the basal concentration of isomaltose resulting from the enzymatic hydrolysis of polymeric 1,6-linked glucose in 238 routine doping control samples. In addition the concentration of dextran measured as isomaltose was estimated in seven urine specimens obtained from patients treated with dextran. Calibration curves for dextran were linear and reproducible. The inter- and intra-assay coefficients of variation for dextran ranged from 4.9 to 7.3% at three concentration levels between 53 and 1186 microg/mL. Recovery ranged from 97 to 112% (mean 106.9%). The assay limit of detection was 3.8 microg/mL and the lower limit of quantification was 12.5 microg/mL. In 96% of the investigated doping control samples, the concentrations of isomaltose were below the LLOQ of 12.5 microg/mL. Even the highest concentrations were approximately 100-300-fold lower than concentrations found in urine samples of patients after intravenous application of dextran. The presented results demonstrate the capability and reliability of the developed LC-MS/MS method for the identification and quantification of dextran in human urine and can be regarded as a method revealing the misuse of dextran in sports.
DOI: 10.1002/bmc.509
Growth control of the eukaryote cell: a systems biology study in yeast.
Author: Castrillo JI, Zeef LA, Hoyle DC, Zhang N, Hayes A, Gardner DC, Cornell MJ, Petty J, Hakes L, Wardleworth L, Rash B, Brown M, Dunn WB, Broadhurst D, O'Donoghue K, Hester SS, Dunkley TP, Hart SR, Swainston N, Li P, Gaskell SJ, Paton NW, Lilley KS, Kell DB, Oliver SG.
Abstract: <h4>Background</h4>Cell growth underlies many key cellular and developmental processes, yet a limited number of studies have been carried out on cell-growth regulation. Comprehensive studies at the transcriptional, proteomic and metabolic levels under defined controlled conditions are currently lacking.<h4>Results</h4>Metabolic control analysis is being exploited in a systems biology study of the eukaryotic cell. Using chemostat culture, we have measured the impact of changes in flux (growth rate) on the transcriptome, proteome, endometabolome and exometabolome of the yeast Saccharomyces cerevisiae. Each functional genomic level shows clear growth-rate-associated trends and discriminates between carbon-sufficient and carbon-limited conditions. Genes consistently and significantly upregulated with increasing growth rate are frequently essential and encode evolutionarily conserved proteins of known function that participate in many protein-protein interactions. In contrast, more unknown, and fewer essential, genes are downregulated with increasing growth rate; their protein products rarely interact with one another. A large proportion of yeast genes under positive growth-rate control share orthologs with other eukaryotes, including humans. Significantly, transcription of genes encoding components of the TOR complex (a major controller of eukaryotic cell growth) is not subject to growth-rate regulation. Moreover, integrative studies reveal the extent and importance of post-transcriptional control, patterns of control of metabolic fluxes at the level of enzyme synthesis, and the relevance of specific enzymatic reactions in the control of metabolic fluxes during cell growth.<h4>Conclusion</h4>This work constitutes a first comprehensive systems biology study on growth-rate control in the eukaryotic cell. The results have direct implications for advanced studies on cell growth, in vivo regulation of metabolic fluxes for comprehensive metabolic engineering, and for the design of genome-scale systems biology models of the eukaryotic cell.
DOI: 10.1186/jbiol54
A kinetic model for the hydrolysis and synthesis of maltose, isomaltose, and maltotriose by glucoamylase.
Author: Beschkov V, Marc A, Engasser JM.
Abstract: Kinetic results on the glucomylase-catalysed hydrolysis of maltose and maltotriose, and glucose polymerization into maltose and isomaltose up to 450 g/L total sugar concentration are presented. Whereas the enzyme has a faster hydrolytic and synthetic activity on alpha-(1-->4) than on alpha-(1-->6) linkages, at equilibrium, on the contrary, the isomaltose level which represents 15% (w/w) of the total sugar concentration at the highest investigated concentrations is much higher than the corresponding maltose level. Under a wide range of initial conditions, experimental results are adequately described by a new kinetic model with simple first- and second-order, or Michaelian-type, rate expressions for the reversible hydrolysis of maltotriose, maltose, and isomaltose. The model also accounts for the inhibition of hydrolysis by glucose, but does not consider the concentration of water which, under the present conditions, was not found kinetically limiting.
Kinetics of formation of maltose and isomaltose through condensation of glucose by glucoamylase.
Author: Adachi S, Ueda Y, Hashimoto K.
Abstract: A kinetic model was devised for the hydrolysis and synthesis of maltose and isomaltose by two glucoamylases from Rhizopus niveus and Aspergillus niger, and the validity of the model was verified experimentally at 313 K and pH 5.0. For both enzymes, the formations of maltose and isomaltose from glucose were parallel reversible reactions, and glucosyl transfer between maltose and isomaltose was not observed. The enzymes catalyzed rapid hydrolysis and synthesis of maltose. Isomaltose was hydrolyzed and synthesized more slowly, but the level produced from glucose was much higher than that of maltose. These hydrolysis and condensation reactions were expressed well by the model.
Isomaltose production by modification of the fructose-binding site on the basis of the predicted structure of sucrose isomerase from "Protaminobacter rubrum".
Author: Lee HC, Kim JH, Kim SY, Lee JK.
Abstract: "Protaminobacter rubrum" sucrose isomerase (SI) catalyzes the isomerization of sucrose to isomaltulose and trehalulose. SI catalyzes the hydrolysis of the glycosidic bond with retention of the anomeric configuration via a mechanism that involves a covalent glycosyl enzyme intermediate. It possesses a (325)RLDRD(329) motif, which is highly conserved and plays an important role in fructose binding. The predicted three-dimensional active-site structure of SI was superimposed on and compared with those of other alpha-glucosidases in family 13. We identified two Arg residues that may play important roles in SI-substrate binding with weak ionic strength. Mutations at Arg(325) and Arg(328) in the fructose-binding site reduced isomaltulose production and slightly increased trehalulose production. In addition, the perturbed interactions between the mutated residues and fructose at the fructose-binding site seemed to have altered the binding affinity of the site, where glucose could now bind and be utilized as a second substrate for isomaltose production. From eight mutant enzymes designed based on structural analysis, the R(325)Q mutant enzyme exhibiting high relative activity for isomaltose production was selected. We recorded 40.0% relative activity at 15% (wt/vol) additive glucose with no temperature shift; the maximum isomaltose concentration and production yield were 57.9 g liter(-1) and 0.55 g of isomaltose/g of sucrose, respectively. Furthermore, isomaltose production increased with temperature but decreased at a temperature of >35 degrees C. Maximum isomaltose production (75.7 g liter(-1)) was recorded at 35 degrees C, and its yield for the consumed sucrose was 0.61 g g(-1) with the addition of 15% (wt/vol) glucose. The relative activity for isomaltose production increased progressively with temperature and reached 45.9% under the same conditions.
DOI: 10.1128/aem.00181-08
Kinetics of condensation of glucose into maltose and isomaltose in hydrolysis of starch by glucoamylase.
Author: Shiraishi F, Kawakami K, Kusunoki K.
Abstract: Kinetics of the condensation of glucose into maltose and isomaltose in the hydrolysis of starch by two types of glucoamylase (from Aspergillus niger and Rhizopus niveus) was studied both experimentally and theoretically. A kinetic model for the hydrolysis of starch by glucoamylase from A. niger was proposed. In this model the reversible hydrolysis of maltose and isomaltose and the kinetic parameters change were taken into consideration. Calculated values agreed approximately with the experimental results, and this simple kinetic model was found to have practical use. The rate of condensation of glucose into isomaltose by enzyme from A. niger was about three times larger than that by enzyme from R. niveus. At a higher initial concentration of starch a large amount of isomaltose was reversed, and the glucose yield was reduced significantly after very long reaction times.
The (alpha-1,6) glycosidic bond of isomaltose: a tricky system for theoretical conformational studies.
Author: Javaroni F, Ferreira AB, da Silva CO.
Abstract: Stable conformations of beta-isomaltose (alpha-D-glucopyranosyl-(1-->6)-beta-D-glucose) in gas-phase and aqueous solution are investigated in this study using quantum mechanical calculations. Conformational maps are calculated at HF/6-31G(d,p) level and lower energy structures are sampled in the most stable regions. Entropic and thermal corrections are considered and the Boltzmann population is obtained for conformers that are representative of the 18 most stable regions found on the potential energy surface. B3LYP/6-31+G(d,p) and B3LYP/6-311+G(2d,2p) calculations are used in conformational samplings. Solvation effects are considered through the polarizable continuum model approach. Hydroxymethyl group orientations are investigated for the most stable conformers. The influence of electronic correlation and solvation on the glycosidic linkage preference (TG, GT, and GG) and hydroxymethyl group orientation (tg, gt, and gg) are discussed. Heteronuclear spin coupling constants ((3)J(C,H)) along the glycosidic linkage are calculated and comparison with other theoretical results and experiments is used to validate the obtained structures.
Cancer: Multifunctional nanodevice reverses drug resistance.
Inhibition by maltose, isomaltose, and nigerose of the synthesis of high-molecular-weight D-glucans by the D-glucosyltransferases of Streptococcus sobrinus.
Author: McAlister D, Doyle RJ, Taylor KG.
Abstract: Two D-glucosyltransferases are produced by Streptococcus sobrinus C211. One (GTF-S) catalyzes the conversion of sucrose into soluble alpha-(1----6)-linked alpha-(1----3)-branched D-glucans, and the other (GTF-I), of sucrose into alpha-(1----3)-linked alpha-(1----6)-branched D-glucans. These enzymes were studied by using maltose, isomaltose, and nigerose as inhibitors. Maltose and isomaltose were found to be competitive inhibitors of GTF-S, whereas nigerose has no effect on GTF-S activity. The Ki values for maltose and isomaltose were determined to be 11 and 15mM, respectively. Maltose, isomaltose, and nigerose competitively inhibit GTF-I. The Ki values for these inhibitors were found to be approximately 0.8, 2.5, and 15mM, respectively. The inhibitory properties of each disaccharide are interpreted in terms of conformational comparisons with sucrose.
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A nasal swelling revealing a metastatic testicular extranodal NK/T-cell lymphoma: A case report and a review of literature.
Author: Tombet CA, El Houmaidi A, Aynaou M, Mhanna T, Chennoufi M, Barki A.
Abstract: Testicular ENKTCL is a rare disease. Asia is the most affected. Primary testicular NK/T-cell lymphoma is rare. Metastases are early and the prognosis is poor. Metastases mainly involve the lymph nodes, skin, contralateral testis, bone marrow, spleen and central nervous system. Nasal metastasis giving rise to bifocal presentation is extremely rare. We report the management of a patient initially seen for a nasal swelling with a hidden history of scrotal swelling, in whom nasal biopsies as well as the analysis of the orchidectomy part made it possible to retain the diagnosis of ENKTCL of the testis with a nasal metastasis.
A Review of the Diagnosis and Management of Premalignant Pancreatic Cystic Lesions.
Author: Keane MG, Afghani E.
Abstract: Pancreatic cystic lesions are an increasingly common clinical finding. They represent a heterogeneous group of lesions that include two of the three known precursors of pancreatic cancer, intraductal papillary mucinous neoplasms (IPMN) and mucinous cystic neoplasms (MCN). Given that approximately 8% of pancreatic cancers arise from these lesions, careful surveillance and timely surgery offers an opportunity for early curative resection in a disease with a dismal prognosis. This review summarizes the current evidence and guidelines for the diagnosis and management of IPMN/MCN. Current pre-operative diagnostic tests in pancreatic cysts are imperfect and a proportion of patients continue to undergo unnecessary surgical resection annually. Balancing cancer prevention while preventing surgical overtreatment, continues to be challenging when managing pancreatic cysts. Cyst fluid molecular markers, such as KRAS, GNAS, VHL, PIK3CA, SMAD4 and TP53, as well as emerging endoscopic technologies such as needle-based confocal laser endomicroscopy and through the needle microbiopsy forceps demonstrate improved diagnostic accuracy. Differences in management and areas of uncertainty between the guidelines are also discussed, including indications for surgery, surveillance protocols and if and when surveillance can be discontinued.
DOI: 10.3390/jcm10061284
Single-mode characteristic of a supermode microcavity Raman laser.
Author: Zhang PJ, Ji QX, Cao QT, Wang H, Liu W, Gong Q, Xiao YF.
Abstract: Microlasers in near-degenerate supermodes lay the cornerstone for studies of non-Hermitian physics, novel light sources, and advanced sensors. Recent experiments of the stimulated scattering in supermode microcavities reported beating phenomena, interpreted as dual-mode lasing, which, however, contradicts their single-mode nature due to the clamped pump field. Here, we investigate the supermode Raman laser in a whispering-gallery microcavity and demonstrate experimentally its single-mode lasing behavior with a side-mode suppression ratio (SMSR) up to 37 dB, despite the emergence of near-degenerate supermodes by the backscattering between counterpropagating waves. Moreover, the beating signal is recognized as the transient interference during the switching process between the two supermode lasers. Self-injection is exploited to manipulate the lasing supermodes, where the SMSR is further improved by 15 dB and the laser linewidth is below 100 Hz.
Building a Learning Health System: Creating an Analytical Workflow for Evidence Generation to Inform Institutional Clinical Care Guidelines.
Author: Dash D, Gokhale A, Patel BS, Callahan A, Posada J, Krishnan G, Collins W, Li R, Schulman K, Ren L, Shah NH.
Abstract: <h4>Background</h4>One key aspect of a learning health system (LHS) is utilizing data generated during care delivery to inform clinical care. However, institutional guidelines that utilize observational data are rare and require months to create, making current processes impractical for more urgent scenarios such as those posed by the COVID-19 pandemic. There exists a need to rapidly analyze institutional data to drive guideline creation where evidence from randomized control trials are unavailable.<h4>Objectives</h4>This article provides a background on the current state of observational data generation in institutional guideline creation and details our institution's experience in creating a novel workflow to (1) demonstrate the value of such a workflow, (2) demonstrate a real-world example, and (3) discuss difficulties encountered and future directions.<h4>Methods</h4>Utilizing a multidisciplinary team of database specialists, clinicians, and informaticists, we created a workflow for identifying and translating a clinical need into a queryable format in our clinical data warehouse, creating data summaries and feeding this information back into clinical guideline creation.<h4>Results</h4>Clinical questions posed by the hospital medicine division were answered in a rapid time frame and informed creation of institutional guidelines for the care of patients with COVID-19. The cost of setting up a workflow, answering the questions, and producing data summaries required around 300 hours of effort and $300,000 USD.<h4>Conclusion</h4>A key component of an LHS is the ability to learn from data generated during care delivery. There are rare examples in the literature and we demonstrate one such example along with proposed thoughts of ideal multidisciplinary team formation and deployment.
Continuous Glucose Monitoring in Women with Normal OGTT in Pregnancy.
Author: Tartaglione L, di Stasio E, Sirico A, Di Leo M, Caputo S, Rizzi A, Caneschi A, De Carolis S, Pitocco D, Lanzone A.
Abstract: Continuous glucose monitoring (CGM) might be an effective tool to improve glycemic control in gestational diabetes mellitus (GDM). Few data are available about its utilization as a diagnostic tool to find potential alterations of glycemia in subjects with normal oral glucose tolerance test (OGTT). In this preliminary prospective real-life observational study, we aimed to analyze the glycemic pattern in normal and gestational diabetes mellitus (GDM) women by continuous glucose monitoring (CGM) in order to detect potential differences between the two groups and glycemic alterations despite a normal OGTT. After the screening for GDM, subjects were connected to a CGM system for seven consecutive days. The areas under the curve of the first 60 minutes after each meal and 60 minutes before breakfast were analyzed. Women with normal OGTT that during CGM showed impaired glycemic values (more than 95 fasting or more than 140 one hour after meals or more than 120 two hours after meals) performed one week of self-monitoring of blood glucose (SMBG). After OGTT, 53 women considered normal and 46 affected by GDM were included. CGM parameters did not show any differences between the two groups with impaired glycemic excursions found in both groups. After CGM period, 33 women with normal OGTT showed abnormal glycemic patterns. These 33 women then performed one week of SMBG. After evaluation of one week of SMBG, 21 required diet therapy and 12 required insulin treatment and were followed until the delivery. An increase in gestational weight gain was observed in normal women with normal OGTT but this was not significant. No significant data were found regarding neonatal outcomes in the two groups of women. In conclusion, CGM use in pregnancy might help to detect glycemic fluctuations in women with normal OGTT, improving their treatment and outcomes.
DOI: 10.1155/2021/9987646