Maltodecaose

The Ruminococcus bromii amylosome protein Sas6 binds single and double helical alpha-glucan structures in starch.[Pubmed:38177679]

Nat Struct Mol Biol. 2024 Feb;31(2):255-265.

Resistant starch is a prebiotic accessed by gut bacteria with specialized amylases and starch-binding proteins. The human gut symbiont Ruminococcus bromii expresses Sas6 (Starch Adherence System member 6), which consists of two starch-specific carbohydrate-binding modules from family 26 (RbCBM26) and family 74 (RbCBM74). Here, we present the crystal structures of Sas6 and of RbCBM74 bound with a double helical dimer of Maltodecaose. The RbCBM74 starch-binding groove complements the double helical alpha-glucan geometry of amylopectin, suggesting that this module selects this feature in starch granules. Isothermal titration calorimetry and native mass spectrometry demonstrate that RbCBM74 recognizes longer single and double helical alpha-glucans, while RbCBM26 binds short maltooligosaccharides. Bioinformatic analysis supports the conservation of the amylopectin-targeting platform in CBM74s from resistant-starch degrading bacteria. Our results suggest that RbCBM74 and RbCBM26 within Sas6 recognize discrete aspects of the starch granule, providing molecular insight into how this structure is accommodated by gut bacteria.

Structural characterization and immunological activities of the water-soluble oligosaccharides isolated from the Panax ginseng roots.[Pubmed:22183124]

Planta. 2012 Jun;235(6):1289-97.

Water-soluble ginseng oligosaccharides (designated as WGOS) with a degree of polymerization ranging from 2 to 10 were obtained from warm-water extract of Panax ginseng roots, and fractionated into five purified fractions (i.e., WGOS-0, WGOS-1, WGOS-2, WGOS-3, and WGOS-4) by gel-filtration chromatography. In order to ascertain the monosaccharide residues in the WGOS, a technique that combines acid hydrolysis and high-performance liquid chromatography was employed. It was found that only glucose residues were present in the WGOS. Fourier transform infrared spectroscopy and electrospray ionization tandem mass spectrometry provided the sequence, linkage, and configuration information. It is noteworthy that alpha-Glcp-(1 --> 6)-alpha-Glcp, alpha-Glcp-(1 --> 6)-alpha-Glcp-(1 --> 4)-alpha-Glcp, alpha-Glcp-(1 --> 6)-alpha-Glcp-(1 --> 6)-alpha-Glcp-(1 --> 4)-alpha-Glcp, and other six malto-oligosaccharides (i.e., maltopentaose, maltohexaose, maltoheptaose, maltooctaose, maltononaose, and Maltodecaose) were detected in ginseng. Preliminary immunological tests in vitro indicated that WGOS were potent B and T-cell stimulators and WGOS-1 has the highest immunostimulating effect on lymphocyte proliferation among those purified fractions. It is hoped that the WGOS will be developed into functional food or medicine.

Molecular dynamics calculations on amylose fragments. I. Glass transition temperatures of maltodecaose at 1, 5, 10, and 15.8% hydration.[Pubmed:11786998]

Biopolymers. 2002 Feb;63(2):99-110.

Molecular dynamics simulations (NPT ensembles, 1 atm) using the all atom force field AMB99C (F. A. Momany and J. L. Willett, Carbohydrate Research, Vol. 326, pp 194-209 and 210-226), are applied to a periodic cell containing ten Maltodecaose fragments and TIP3P water molecules. Simulations were carried out at 25 K intervals over a range of temperatures above and below the expected glass transition temperature, T(g), for different water concentrations. The amorphous cell was constructed through successive dynamic equilibration steps at temperatures above T(g) and the temperature lowered until several points of reduced slope (1/T vs volume) were obtained. This procedure was carried out at each hydration level. Each dynamics simulation was continued until the volume remained constant without up or down drift for at least the last 100 ps. For a given temperature, most simulations required 400-600 ps to reach an equilibrium state, but longer times were necessary as the amount of water in the cell was reduced. A total of more than 30 ns of simulations were required for the complete study. The T(g) for each hydrated cell was taken as that point at which a discontinuity in slope of the volume (V), potential energy (PE), or density (rho) vs 1/T was observed. The average calculated T(g) values were 311, 337, 386, and 477 K for hydration levels of 15.8, 10, 5, and 1%, respectively, in generally good agreement with experimental values. The T(g) for anhydrous amylose is above the decomposition temperature for carbohydrates and so cannot be easily measured. However, it has also been difficult to obtain a value of T(g) for anhydrous amylose using simulation methods. Other molecular parameters such as end-to-end distances, mean square distributions, and pair distributions are discussed.

An increase in the transglycosylation activity of Saccharomycopsis alpha-amylase altered by site-directed mutagenesis.[Pubmed:2029542]

Biochim Biophys Acta. 1991 Apr 29;1077(3):416-9.

The 84th tryptophan residue in Saccharomycopsis alpha-amylase molecule was replaced by a leucine residue and the resulting site-directed mutant, W84L enzyme, showed an increase in transglycosylation activity. At a 40% digestion point of maltoheptaose (G7), for example, maltooligosaccharide products larger than Maltodecaose (G10) amounted to approx. 60% of the total product from the mutant enzyme reaction, whereas no such large products were observed in the native enzyme reaction. Analysis of the reaction products from p-nitrophenyl maltooligosaccharides indicated that these large products were formed by addition of the hydrolysis products on the nonreducing end side to the starting intact substrates. These results suggest that the tryptophan residue located at subsite 3 of the enzyme plays an important role not only to hold the substrate, but also to liberate the hydrolysis products from the substrate binding pocket.

The recognition of maltodextrins by Escherichia coli.[Pubmed:6997044]

Eur J Biochem. 1980 Jul;108(2):631-6.

1. Escherichia coli can accumulate 14C-labelled (alpha 1 leads to 4)-linked D-glucose oligomers up to maltoheptaose. Longer maltodextrins are not transported and are not utilized as carbon sources. 2. Maltodextrins too large to be transported are nevertheless bound by the outer envelope of intact E. coli. This binding is saturable (Kd for Maltodecaose = 3-4 microM) and the binding sites are inducible by maltose. Each bacterium has approximately 30,000 sites when fully induced. 3. Using mutants devoid of various components of the maltose transport system, the high-affinity binding of maltodextrins by intact bacteria has been shown to be dependent on the presence of both lambda receptor (an outer membrane protein) and periplasmic maltose binding protein. 4. The same binding sites are accessible to both utilizable and non-utilizable maltodextrins. Maltodecapentaose is a competitive inhibitor of maltose transport (Ki 1.5-2.5 microM). 5. These results show that the periplasmic maltose binding protein is readily accessible to substrates of at least 2500 molecular weight. The inability to transport dextrins larger than maltoheptaose is, therefore, due to the inability of E. coli to transfer large substrates from the binding protein to the cytoplasm and not to lack of access through the outer membrane.

Lambda receptor in the outer membrane of Escherichia coli as a binding protein for maltodextrins and starch polysaccharides.[Pubmed:6445892]

J Bacteriol. 1980 May;142(2):521-6.

The starch polysaccharides amylose and amylopectin are not utilized by Escherichia coli, but are bound by the bacteria. The following evidence supports the view that the outer membrane lambda receptor protein, a component of the maltose/ maltodextrin transport system is responsible for the binding. (i) Amylose and amylopectin both inhibit the transport of maltose into E. coli. (ii) Both polysaccharides prevent binding of non-utilizable maltodextrins by the intact bacterium, a process previously shown to be dependent on components of the maltose transport system (T. Ferenci, Eur. J. Biochem., in press). (iii) A fluorescent amylopectin derivative, O-(fluoresceinyl thiocarbamoyl)-amylopectin, has been synthesized and shown to bind to E. coli in a reversible, saturable manner. Binding of O-(fluoresceinyl thiocarbamoyl)-amylopectin is absent in mutants lacking the lambda receptor, but mutations in any of the other components of the maltose transport system do not affect binding as long as lambda receptor is present. (iv) Using the inhibition of lambda receptor-dependent O-(fluoresceinyl thiocarbamoyl)-amylopectin binding as an assay, the affinities of the lambda receptor for maltodextrins and other sugars have been estimated. The affinity for dextrins increases with increasing degree of polymerization (K(d) for maltose, 14 mM; for maltotetraose, 0.3 mM; for Maltodecaose, 0.075 mM). Maltose and some other di- and trisaccharides are inhibitory to amylopectin binding, but only at concentrations above 1 mM.

Repetitive attack by Aspergillus oryzae alpha amylase.[Pubmed:306286]

Carbohydr Res. 1978 Mar;61:377-85.

The action of Aspergillus oryzae alpha amylase on reducing-end, and uniformly radiolabeled maltotriose through Maltodecaose has been studied. The enzyme is found to hydrolyze more than a single glycosidic bond during enzyme-substrate encounters. The extent of this repetitive attack is quantitated.