IsoMaltose

NMR Quantification of Carbohydrates in Complex Mixtures. A Challenge on Honey.[Pubmed:29110461]

Anal Chem. 2017 Dec 19;89(24):13405-13414.

The knowledge of carbohydrate composition is greatly important to determine the properties of natural matrices such as foodstuff and food ingredients. However, because of the structural similarity and the multiple isomeric forms of carbohydrates in solution, their analysis is often a complex task. Here we propose an NMR analytical procedure based on highly selective chemical shift filters followed by TOCSY, which allows us to acquire specific background-free signals for each sugar. The method was tested on raw honey samples dissolved in water with no other pretreatment. In total, 22 sugars typically found in honey were quantified: 4 monosaccharides (glucose, fructose, mannose, rhamnose), 11 disaccharides (sucrose, trehalose, turanose, maltose, maltulose, palatinose, melibiose and melezitose, IsoMaltose, gentiobiose nigerose, and kojibiose), and 7 trisaccharides (raffinose, isomaltotriose, erlose, melezitose, maltotriose, panose, and 1-kestose). Satisfactory results in terms of limit of quantification (0.03-0.4 g/100g honey), precision (% RSD: 0.99-4.03), trueness (bias % 0.4-4.2), and recovery (97-104%) were obtained. An accurate control of the instrumental temperature and of the sample pH endows an optimal chemical shift reproducibility, making the procedure amenable to automation and suitable to routine analysis. While validated on honey, which is one of the most complex natural matrices in terms of saccharides composition, this innovative approach can be easily transferred to other natural matrices.

Extending the Scope of GTFR Glucosylation Reactions with Tosylated Substrates for Rare Sugars Synthesis.[Pubmed:28796424]

Chembiochem. 2017 Oct 18;18(20):2012-2015.

Functionalized rare sugars were synthesized with 2-, 3-, and 6-tosylated glucose derivatives as acceptor substrates by transglucosylation with sucrose and the glucansucrase GTFR from Streptococcus oralis. The 2- and 3-tosylated glucose derivatives yielded the corresponding 1,6-linked disaccharides (IsoMaltose analogues), whereas the 6-tosylated glucose derivatives resulted in 1,3-linked disaccharides (nigerose analogue) with high regioselectivity in up to 95 % yield. Docking studies provided insight into the binding mode of the acceptors and suggested two different orientations that were responsible for the change in regioselectivity.

Enzymatic Synthesis and Structural Characterization of Theanderose through Transfructosylation Reaction Catalyzed by Levansucrase from Bacillus subtilis CECT 39.[Pubmed:29131629]

J Agric Food Chem. 2017 Dec 6;65(48):10505-10513.

This work addresses the high-yield and fast enzymatic production of theanderose, a naturally occurring carbohydrate, also known as isomaltosucrose, whose chemical structure determined by NMR is alpha-d-glucopyranosyl-(1 --> 6)-alpha-d-glucopyranosyl-(1 --> 2)-beta-d-fructofuranose. The ability of IsoMaltose to act as an acceptor in the Bacillus subtilis CECT 39 levansucrase-catalyzed transfructosylation reaction to efficiently produce theanderose in the presence of sucrose as a donor is described by using four different sucrose:IsoMaltose concentration ratios. The maximum theanderose concentration ranged from 122.4 to 130.4 g L(-1), was obtained after only 1 h and at a moderate temperature (37 degrees C), leading to high productivity (109.7-130.4 g L(-1)h(-1)) and yield (up to 37.3%) values. The enzymatic synthesis was highly regiospecific, since no other detectable acceptor reaction products were formed. The development of efficient and cost-effective procedures for the biosynthesis of unexplored but appealing oligosaccharides as potential sweeteners, such as theanderose, could help to expand its potential applications which are currently limited by their low availability.

Synthesis of Isomalto-Oligosaccharides by Pichia pastoris Displaying the Aspergillus niger alpha-Glucosidase.[Pubmed:28980463]

J Agric Food Chem. 2017 Nov 1;65(43):9468-9474.

We explored the ability of an Aspergillus niger alpha-glucosidase displayed on P. pastoris to act as a whole-cell biocatalyst (Pp-ANGL-GCW61) system to synthesize isomalto-oligosaccharides (IMOs). IMOs are a mixture that includes IsoMaltose (IG2), panose (P), and isomaltotriose (IG3). In this study, the IMOs were synthesized by a hydrolysis-transglycosylation reaction in an aqueous system of maltose. In a 2 mL reaction system, the IMOs were synthesized with a conversion rate of approximately 49% in 2 h when 30% maltose was utilized under optimal conditions by Pp-ANGL-GCW61. Additionally, the 0.5-L reaction system was conducted in a 2-L stirred reactor with a conversion rate of approximately 44% in 2 h. Moreover, the conversion rate was relatively stable after the whole-cell catalyst was reused three times. In conclusion, Pp-ANGL-GCW61 has a high reaction efficiency and operational stability, which makes it a powerful biocatalyst available for industrial scale synthesis.

Structures of jacalin-related lectin PPL3 regulating pearl shell biomineralization.[Pubmed:29524263]

Proteins. 2018 Jun;86(6):644-653.

The nacreous layer of pearl oysters is one of the major biominerals of commercial and industrial interest. Jacalin-related lectins, including PPL3 isoforms, are known to regulate biomineralization of the Pteria penguin pearl shell, although the molecular mechanisms are largely unknown. The PPL3 crystal structures were determined partly by utilizing microgravity environments for 3 isoforms, namely, PPL3A, PPL3B, and PPL3C. The structures revealed a tail-to-tail dimer structure established by forming a unique inter-subunit disulfide bond at C-termini. The N-terminal residues were found in pyroglutamate form, and this was partly explained by the post-translational modification of PPL3 isoforms implied from the discrepancy between amino acid and gene sequences. The complex structures with trehalose and IsoMaltose indicated that the novel specificity originated from the unique alpha-helix of PPL3 isoforms. Docking simulations of PPL3B to various calcite crystal faces suggested the edge of a beta-sheet and the carbohydrate-binding site rich in charged residues were the interface to the biomineral, and implied that the isoforms differed in calcite interactions.

Isomaltose is composed of two glucose units and suitable as a non-cariogenic sucrose replacement and is favorable in products for diabetics and prediabetic dispositions.

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