Isomaltooctaose

Structural elucidation of the cyclization mechanism of alpha-1,6-glucan by Bacillus circulans T-3040 cycloisomaltooligosaccharide glucanotransferase.[Pubmed:24616103]

J Biol Chem. 2014 Apr 25;289(17):12040-12051.

Bacillus circulans T-3040 cycloisomaltooligosaccharide glucanotransferase belongs to the glycoside hydrolase family 66 and catalyzes an intramolecular transglucosylation reaction that produces cycloisomaltooligosaccharides from dextran. The crystal structure of the core fragment from Ser-39 to Met-738 of B. circulans T-3040 cycloisomaltooligosaccharide glucanotransferase, devoid of its N-terminal signal peptide and C-terminal nonconserved regions, was determined. The structural model contained one catalytic (beta/alpha)8-barrel domain and three beta-domains. Domain N with an immunoglobulin-like beta-sandwich fold was attached to the N terminus; domain C with a Greek key beta-sandwich fold was located at the C terminus, and a carbohydrate-binding module family 35 (CBM35) beta-jellyroll domain B was inserted between the 7th beta-strand and the 7th alpha-helix of the catalytic domain A. The structures of the inactive catalytic nucleophile mutant enzyme complexed with isomaltohexaose, isomaltoheptaose, Isomaltooctaose, and cycloIsomaltooctaose revealed that the ligands bound in the catalytic cleft and the sugar-binding site of CBM35. Of these, Isomaltooctaose bound in the catalytic site extended to the second sugar-binding site of CBM35, which acted as subsite -8, representing the enzyme.substrate complex when the enzyme produces cycloIsomaltooctaose. The isomaltoheptaose and cycloIsomaltooctaose bound in the catalytic cleft with a circular structure around Met-310, representing the enzyme.product complex. These structures collectively indicated that CBM35 functions in determining the size of the product, causing the predominant production of cycloIsomaltooctaose by the enzyme. The canonical sugar-binding site of CBM35 bound the mid-part of isomaltooligosaccharides, indicating that the original function involved substrate binding required for efficient catalysis.

Specificity of the glucan-binding lectin of Streptococcus cricetus.[Pubmed:3397177]

Infect Immun. 1988 Aug;56(8):1864-72.

The specificity of the glucan-binding lectin (GBL) of Streptococcus cricetus AHT was determined. Examination of the kinetics of aggregation of cell suspensions with glucans containing various percentages of alpha-1,6, alpha-1,4, alpha-1,3, and alpha-1,2 anomeric linkages revealed that only glucans with at least 80% alpha-1,6 linkages promoted strong aggregation. Moreover, only linear glucans with molecular weights greater than 5 X 10(5) were capable of causing rapid aggregation of the bacteria. The lectin was observed to be present on S. cricetus strains, on Streptococcus sobrinus, and on several Streptococcus mutants strains. Preincubation of suspensions of S. cricetus AHT with glucan T10 (molecular weight of 10,000) before the addition of high-molecular-weight glucan resulted in competitive inhibition in a concentration-dependent manner. Inhibition was achieved also with isomaltopentaose, isomaltohexaose, and Isomaltooctaose, but at higher concentrations than glucan T10. In contrast, no inhibition was observed with maltoheptaose, providing additional evidence for the specificity of GBL. Treatment of suspensions of S. cricetus AHT with trypsin before and after aggregation with high-molecular-weight glucan revealed a substantial level of protection of GBL when in a bound state. Collectively, these results indicated that GBL has an absolute affinity for glucans rich in alpha-1,6 linkages and possesses an active site which recognizes internal sequences and accommodates isomaltosaccharides of at least nine residues. This unusual specificity may contribute to the colonization of S. cricetus, S. sobrinus, and S. mutans in glucan-containing plaque in the oral cavity.

[Test of cellulose and cellulose derivatives for carcinogenic activity in rats, mice and rabbits].[Pubmed:4460953]

Arch Geschwulstforsch. 1974;44(3):222-34.

Activated cellulose, p-aminobenzylcellulose, p-hydroxybenzylcellulose, cellulose-m-aminobenzoxymethylether and cellulose-m-hydroxybenzoxymethylether which are used as highmolecular inert components for the preparation of immunoadsorbents, have been tested for carcinogenic activity in Wistar-rats and CBA-mice by the subcutaneous and intramuscular route of administration. In the same manner the coupling products have been tested in rats, mice and rabbits of diazotized p-aminobenzylcellulose and cellulose-m-aminobenzoxymethylether with a) human gammaglobulin [(cellulose-p-benzylether)-azogammaglobulin and (cellulose-m-benzoxymethylether)-azogammaglobulin respectively] and b) 1-(m-hydroxyphenyl)-flavozole derivatives of saccharides of the isomaltodextrin- and maltodextrin series [saccharide-1-(3 ft.-hydroxy-4 ft.-(resp.-6 ft.-or-2 ft.-) [cellulose-p-benzylether]-azophenyl)-flavazoles and saccharide-1-(3 ft.-hydroxy-4 ft.-(resp. -6 ft;-or-2 ft.-) [cellulose-m-benzoxymethylether]-azophenyl)-flavazoles with isomaltotriose, isomaltotetraose, isomaltopentaose, isomaltohexaose, Isomaltooctaose, maltotriose, maltotetraose, maltopentaose, maltohexaose and maltooctaose as saccharide moieties]. No tumours were found in rabbits. No statistical significant difference could be stated between the tumour incidence of experimental animals and controls in the rat and mouse groups.