Studies on dextranases. 3. Insolubilization of a bacterial dextranase

Ammonium hydroxide treatment of 1,6:2,3-dianhydro-4-O-benzyl-β-D-mannopyranose, followed by acetylation, gave 2-acetamido-3-O-acetyl-1,6-anhydro-4-O-benzyl-2-deoxy-β-D-glucopyranose which was catalytically reduced to give 2-acetamido-3-O-acetyl-1,6-anhydro-2-deoxy-β-D-glucopyranose (6), the starting material for the synthesis of (1→4)-linked disaccharides bearing a 2-acetamido-2-deoxy-D-glucopyranose reducing residue. Selective benzylation of 2-acetamido-1,6-anhydro-2-deoxy-β-D-glucopyranose gave a mixture of the 3,4-di-O-benzyl derivative and the two mono-O-benzyl derivatives, the 4-O-benzyl being preponderant. The latter derivative was acetylated, to give a compound identical with that just described. For the purpose of comparison, 2-acetamido-4-O-acetyl-1,6-anhydro-2-deoxy-β-D-glucopyranose has been prepared by selective acetylation of 2-acetamido-1,6-anhydro-2-deoxy-β-D-glucopyranose.Condensation between 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide and 6 gave, after acetolysis of the anhydro ring, the peracetylated derivative (17) of 2-acetamido-2-deoxy-4-O-β-D-glucopyranosyl-α-D-glucopyranose. A condensation of 6 with 3,4,6-tri-O-acetyl-2-deoxy-2-diphenoxyphosphorylamino-α-D-glucopyranosyl bromide likewise gave, after catalytic hydrogenation, acetylation, and acetolysis, the peracylated derivative (21) of di-N-acetylchitobiose.     

Hydrolysis of streptococcal polysaccharides by micromycete dextranases

The effect of dextranase enzyme preparations obtained from Penicillium piscarium BIM G-102, Penicillium funiculosum, Aspergillus insuetus G-116 and Aspergillus ustus on polysaccharides synthesized by cariesogenic Streptococcus sanguis and Streptococcus mitis was being studied. According to the data obtained dextranases from P. piscarium, P. funiculosum and Asp. ustus can be considered as a promising anticarious agent.     

Thermostable dextranases: screening, detection and preliminary characterization

Screening methods have been developed for detection of micro-organisms producing thermostable dextranases. They utilize the incorporation of Blue Dextran into agar or liquid culture media for isolation of active dextranase producers growing at temperatures above 55°C. A variety of high temperature environments in sugar factories and naturally occurring thermal water samples were excellent sources of dextranase producers. A number of aerobic and anaerobic thermophilic bacteria, isolated from these sources, were found to produce thermostable dextranases. Dextranases with the greatest thermostability were found in cultures of anaerobic bacteria grown above 65°C. Temperature optima were determined for several crude enzyme preparations, four of which exhibited temperature optima in the range 65–85°C.     

Studies on dextranases. IV. Mode of action of dextranase D1 on oligosaccharides

The products of action of a purified, extracellular endo-dextranase D₁, isolated from a new species of Pseudomonas, on pure isomaltose oligosaccharides have been investigated. Reduced and tritiated oligosaccharides have also been studied, and a model is postulated for the enzyme active-site, based on substrate specificity.     

Studies on dextrans and dextranases. XI. The structure of a dextran elaborated by Leuconostoc mesenteroides NRRL B-1299

The synthesis of di-(6-deoxy-β-D-allofuranose) 1,5′:1′,5-dianhydride (8) from 6-deoxy-D-allose is described. Periodate oxidation of 8, followed by borohydride reduction and acetylation, yielded a crystalline 2,4,7,9-tetra(acetoxymethyl)-5.10-dimethyl-1,3,6,8-tetraoxecane (3).     

Studies on dextrans and dextranases. X. Types and percentages of secondary linkages in the dextrans elaborated by Leuconostoc mesenteroides NRRL B-1299

The water-soluble (dextran S) and less water-soluble (dextran L) dextrans elaborated by Leuconostoc mesenteroides NRRL B-1299 contain α-d-glucopyranose residues linked through positions 1 and 6, 1 and 3, as well as 1, 2, and 6. The approximate number of terminal non-reducing d-glucose residues and those linked through positions 1 and 6, 1 and 3, as well as 1, 2, and 6 in the average repeating-unit of dextran S are 5, 4, 1, and 5. The corresponding figures for dextran L are 5, 4, 3, and 5.     

Multiple dextranases from the yeast <Emphasis Type="Italic">Lipomyces starkeyi</Emphasis>

The soil yeast Lipomyces starkeyi (NCYC 1436) secretes dextranase activity into the growth medium. Resolution of a dextranase-active protein fraction by SDS-PAGE produced three protein bands, of 66 kDa, 68 kDa and 78 kDa, and isoelectric focusing of the same fraction resulted in seven protein bands, of pIs 3.50, 3.85, 4.20, 4.80, 4.85, 5.00 and 5.30. Dextranase activity was demonstrated for all the isoelectric forms, and for the 78 kDa species in the presence of SDS. Amino acid compositions of the 66 kDa, 68 kDa and 78 kDa protein bands were determined, and the N-termini of the 66 kDa and 78 kDa protein bands were sequenced: the first two amino acids at the N-terminus of each protein were alanine and valine, respectively; an alanine-valine pair is seen early in the N-terminal coding sequences of the dextranases and the isopullulanase produced by the phylogenetically disparate organisms contributing to glycosyl hydrolase family 49.     

Brachyptera Group. Sp.32. C. Brachyptera. Sp.33. C.c RUFA. Sp.34. C. Troglodytes. Sp.35. C. Fulvicapilla.

A part from considerations as to where it is best wedged into the linear sequence, the brachyptera group is defined in general terms as a compact group of four small or very small species which resemble one another in many important specific characters and the other thirty-six species classified here as Cisticola in so many ways of form, coloration and behaviour as to make them best understood by classifying them also under that generic name.