Galactofuranosyl residues

Klebsiella K12, pyruvic acid is acetalically linked to 0-5 and 0-6 of a y -D-galactofuranosyl residue. Pyruvic acid is further acetalically linked to 0-4 and 0-5 of a D-mannitol residue in an unusual type of teichoic acid from Brevibacterium iodinum The absolute configuration at the acetalic carbon atom is (S) in the 5. pneumoniae type 4 polysaccharide, but it has not yet been determined for the other polymers. 

L-Arabinose was formed on periodate oxidation, borohydride reduction, and mild, acid hydrolysis of the pentasaccharide, demonstrating that it contains a D-galactofuranosyl residue. The amino sugar residue was resistant to periodate oxidation but was oxidized after N-deacetylation, showing that this residue is substituted at 0-4, not at 0-3. The structure of the pentasaccharide 21 was thereby established. It showed [a]D —36°, indicating that all sugar residues are /3-D-linked. 

Replacement of hydroxyl by benzyloxy gives a- and /3-shifts similar to those of methoxyl, and resonances of the 13C-n.m.r. spectrum of methyl 2,3-di-O-benzyl-a-D-galactofuranoside28 have been found to be sufficiently close to those of a polysaccharide containing 2,3-di-O-substituted a-D-galactofuranosyl residues as to make possible a structural confirmation.17... 

A signal at 8C 109.0, displayed17 by a complex heteropolymer obtained from Klebsiella serotype 40, arose from 2,3-di-O-substituted /3-D-galactofuranosyl residues (see Section VI,14). 

Highly levorotatory polymers were obtained when (58) was polymerized at either —28° or —90°, but no polymerization occurred at —97°. By comparison of the rotations (C ]d —70 to —95° in chloroform) of the polymers formed from (58) with those of the four unmethylated, anomeric methyl o-galactosides, it was concluded that /S-D-galactofuranosyl residues were the preponderant structural units of these polymers. The results of polarimetric measurements during acid hydrolysis of the polymer indicated that pyranosyl residues, also, were probably present. Isolation and characterization of the products from a graded hydrolysis with acid would confirm this contention. 

Fischer, W., Schmidt, M.A., Jann, B. and Jann, K. (1982) Structure of the Escherichia coli K2 capsular antigen. Stereochemical configuration of the glycerol phosphate and distribution of galac-topyranosyl and galactofuranosyl residues. Biochemistry 21 1279-1289... 

Rather uncommon are the two pyruvic acetal structures which have been identified in Klebsiella K12 capsular polysaccharides and in the teichoic acid of bacterium NCTC 9742 [10]. In the former case, a 4,5-0-(l-carboxyethylidene)- -D-galactofuranosyl residue was found at the side chain terminus of the hexa-saccharide repeating unit. In the latter case, the teichoic acid contains intra-catenally bound 2,3-0-(l-carboxyethylidene)-D-mannitol phosphate. No data about the configuration of these pyruvic acetals are available. 

Figure 9. Proposed structure for the carbohydrate part of the proteo-heterogly-can from P. oryzae. All sugar residues are in the a-configuration. The subscripts outside the brackets indicate the average molecular proportion of the various types of side-chains. The order of the sidechains along the backbone is unknown. M indicates an a-D-mannopyranosyl residue, G is an a-D-glucopyranosyl residue, and Galf is an a-v-galactofuranosyl residue (11).

Studies with a mutant (. Charlesii 17D) of charlesii which is incapable of growing in D-galactose showed that the glycopeptide which it secretes into the growth medium contains only about 2 galactofuranosyl residues per molecule and 1 atom of phosphorus (18). A second mutant ( P. charlesii 17B) which contained about 5 galactofuranosyl residues per molecule of glycopeptide also contained only 1 or 2 atoms of phosphorus. 

These results suggest that the incorporation of phosphorus in whatever form it takes may require the presence of a galactofuranosyl residue in that region of the mannan before the phosphorus containing residue can be transferred. The glycopeptide from the 17D mutant contained about one mole of ethanolamine per mole of glycopeptide. 

P. charlesii contain no galactofuranosyl residues (19) and the alkali-soluble, alcohol-insoluble fraction of cell walls of 3-day aerated cultures of charlesii contain only 1.6% galactofuranosyl residues and no detectable mannopyranosyl residues (20). This fraction also contained glucosyl residues and ethanolamine. The results from both laboratories suggest that the cell walls of charlesii contain few galactofuranosyl residues and that the... 

Enzymic and chemical assays, a) Galactofuranosyl-containing chains. Exo-3-D-galactofuranosidase (21) was used to release galactofuranosyl residues from galactan chains and the quantity of galactose released was quantified (28). Controls without substrate or galactofuranosidase or with inactivated enzyme were carried out and appropriate corrections were made. 

Figure 11. Fractionation of polymer on a concanavalin A-Sepharose 4B column. Galactofuranosyl-containing fractions from a Bio-Gel A-5m column were pooled and applied to a column of concanavalin A-Sepharose 4B. The adsorbent was washed successively with 40mM Tris-HCl-40mM NaCl 0.24% deoxycholate, pH 7.5, followed by the same buffer containing 1% methyl-a-o-mannopyranoside starting with Fraction 27. Fractions containing 100 drops were collected and 0.5 mL samples were assayed for galactofuranosyl residues (211 Fractions containing galactofuranosyl residues are indicated with a bar.

Immunochemical studies on galactomannans isolated from the mycelia and culture media of Hormodendrum pedrosoi, H. compactum, and H. dermatitidis have indicated that acid-labile D-galactofuranosyl residues are responsible for precipitating antibodies. The galactomannans and their respective core components precipitated anti-(5. cerevisiae) serum, which interacts only with (1 6)-... 

The capsular polysaccharide of Diplococcus pneumoniae has been shown to possess a linear pentasaccharide repeating unit containing residues of d-glucopyranosyluronic acid, o-galactofuranose, and L-rhamnopyranose (1 2 2). ° The presence of 2,3-linked D-galactofuranosyl residues in the polysaccharide of Klebsiella K41 has been confirmed by the characterization of 5,6-di-O-methyl-D-galactofuranose as a product in the methylation of the polysaccharide, and of the presence of L-arabinose in the Smith degradation... 

An extracellular polysaccharide produced by Aspergillus nidulans is composed of residues of 2-amino-2-deoxy-D-galactose (70%) and o-galactose (15%). A polysaccharide isolated from the ascocarps of Cordyceps sinensis, and containing residues of D-galactose and D-mannose (1 1), has been shown to contain a backbone of (1 - 2)-linked a-D-mannopyranosyl residues with branches composed of (1 3), (1 -> 5)-, and (1 6)-linked D-galactofuranosyl residues... 

---