Staining of extracellular polymeric substances and cells in bioaggregates

Multiple fluorochrome experiments with as many fluorochromes as possible are desired for exploring the detailed structure of bioaggregates. Spectral peak interference and other practical limitations, however, restrict the maximum number of stains used simultaneously to three. This current study proposes a sixfold labelled scheme to stain the total cells, dead cells, proteins, lipids, and α- and β-polysaccharides in bioaggregates. Two aerobic granule systems, the phenol-fed and the acetate-fed granules, were utilized as the testing samples for demonstrating the use of the proposed scheme.     

Use of an α-d-glucosidase for the specific cytochemical identification of lateral α-d-xylosyl end groups in plant xyloglucans

Summary α-Linked d-xylosyl side chains represent the typical feature common to all xyloglucans not shared by other cell wall polysaccharides. Since no easily available α-d-xyloxidase is known, advantage was taken of the conformational and configurational homologies between α-d-xylopyranose and α-d-glucopyranose to make an α-d-glucosidase-gold complex which was able to recognize α-d-xylosyl terminal residues of xyloglucans. This marker was used together with α-l-fucosidase gold complex for the double labeling on two different structural features of the same macromolecule in plant primary cell wall.     

Sucrose phosphorylases catalyze transglycosylation reactions on carboxylic acid compounds

Two sucrose phosphorylases were employed for glycosylation of carboxylic acid compounds. Streptococcus mutans sucrose phosphorylase showed remarkable transglycosylating activity, especially under acidic conditions. Leuconostoc mesenteroides sucrose phosphorylase exhibited very weak transglycosylating activity. Three main products were detected from the reaction mixture using benzoic acid and sucrose as an acceptor and a donor molecule, respectively. These compounds were identified as 1-O-benzoyl α-d-glucopyranoside, 2-O-benzoyl α-d-glucopyranose, and 2-O-benzoyl β-d-glucopyranose by 1D-and 2D-NMR analyses of the isolated products and their acetylated products. Time-course analyses proved that 1-O-benzoyl α-d-glucopyranoside was initially produced by the transglycosylation reaction of the enzyme. 2-O-Benzoyl α-d-glucopyranose and 2-O-benzoyl β-d-glucopyranose were produced from 1-O-benzoyl α-d-glucopyranoside by intramolecular acyl migration reaction. S. mutans sucrose phosphorylase showed broad acceptor-specificity. This sucrose phosphorylase catalyzed transglycosylation to various carboxylic compounds such as short-chain fatty acids, hydroxy acids, dicarboxylic acids, and phenolic carboxylic acids. 1-O-Acetyl α-d-glucopyranoside was also enzymatically synthesized by transglucosylation reaction of the enzyme. The sensory test of acetic acid and the glucosides revealed that the sour taste of acetic acid glucosides was significantly lower than that of acetic acid.     

Production and structure elucidation of di- and oligosaccharide lipids (biosurfactants) from Tsukamurella sp. nov.

The bacterium Tsukamurella sp. nov., isolated from soil, was found to produce novel glycolipids when grown on sunflower oil as the sole carbon source. The glycolipids were isolated by chromatography on silica columns and their structures elucidated using a combination of multidimensional NMR and MS techniques. The three main components are 2,3-di-O-acyl-α-d-glucopyranosyl-(1-1)-α-d-glucopyranose, 2,3-di-O-acyl-β-d-glucopyranosyl-(1-2)-4,6-di-O-acyl-α-d-glucopyranosyl-(1-1)-α-d-glucopyranose and 2,3-di-O-acyl-β-d-glucopyranosyl-(1-2)-β-d-galactopyranosyl-(1-6)-4,6-di-O-acyl-α-d-glucopyranosyl-(1-1)-α-d-glucopyranosl which are linked to fatty acids varying in chain length from C₄ to C₁₈. The glycolipids are mainly extracellular but are also found attached to the cell walls. During the cultivation the composition of the glycolipids changed from disaccharide- to tri- and tetrasaccharide lipids. The glycolipids show good surface-active behaviour and have antimicrobial properties. Received: 22 May 1998 / Received revision: 24 August 1998 / Accepted: 26 August 1998     

Production, purification and structural characterization of an exopolysaccharide produced by a probiotic Lactobacillus plantarum MTCC 9510

Exopolysaccharides (EPS) from lactic acid bacteria contribute to specific rheology and texture of fermented milk products and finds applications even in non-dairy foods and in therapeutics. Box-Behnken model of response surface methodology (RSM) was employed to formulate the production medium for exopolysaccharide (EPS). FT-IR spectral analysis of the purified EPS from Lactobacillus plantarum MTCC 9510 revealed prominent characteristic groups corresponding to polyhydric alcohols. The degradation temperature (Td) of the polysaccharide was found to be 260°C with the help of thermo gravimetric analysis (TGA). Structure elucidation of the EPS showed that it consists of a trisaccharide repeating unit of α-d-glucose, β-d-glucose and α-d-mannose.     

Structural analysis of the exopolysaccharide produced by <Emphasis Type="Italic">Streptococcus thermophilus</Emphasis> ST1 solely by NMR spectroscopy

The use of lactic acid bacteria in fermentation of milk results in favorable physical and rheological properties due to in situ exopolysaccharide (EPS) production. The EPS from S. thermophilus ST1 produces highly viscous aqueous solutions and its structure has been investigated by NMR spectroscopy. Notably, all aspects of the elucidation of its primary structure including component analysis and absolute configuration of the constituent monosaccharides were carried out by NMR spectroscopy. An array of techniques was utilized including, inter alia, PANSY and NOESY-HSQC TILT experiments. The EPS is composed of hexasaccharide repeating units with the following structure: → 3)[α-d-Glcp-(1 → 4)]-β-d-Galp-(1 → 4)-β-d-Glcp-(1 → 4)[β-d-Galf-(1 → 6)]-β-d-Glcp-(1 → 6)-β-d-Glcp-(1 →, in which the residues in square brackets are terminal groups substituting backbone sugar residues that consequently are branch-points in the repeating unit of the polymer. Thus, the EPS consists of a backbone of four sugar residues with two terminal sugar residues making up two side-chains of the repeating unit. The molecular mass of the polymer was determined using translational diffusion experiments which resulted in M_w = 62 kDa, corresponding to 64 repeating units in the EPS.     

Four glycoside hydrolases are differentially modulated by auxins, cytokinins, abscisic acid and gibberellic acid in apple fruit callus cultures

α-l-Arabinofuranosidase, α- and β-d-xylosidase, and β-d-glucosidase activity was detected in the soluble fraction (S-F) extracted with water and in the NaCl-released fraction (NaCl-F) extracted with a high-salt concentration buffer from apple callus cultures. The activity was found to be differentially modulated by the addition of various plant growth regulators (PGRs) to calluses that had lost their requirement for specific PGRs (“habituation” phenomenon). α-l-Arabinofuranosidase activity was 93%, 130%, 126% and 186% higher in the NaCl-F from IAA-, IBA-, ABA- and GA₃-treated callus than in that extracted from untreated callus while S-F α-l-arabinofuranosidase activity was only 71%, 24%, 55% and 66% higher, respectively. α-d-Xylosidase displayed low activity levels in both S-F and NaCl-F but 2iP-treated callus showed higher α-d-xylosidase activity in both fractions than the control. 2,4-D increased α-d-xylosidase activity by 110% in the NaCl-F but decreased it by 40% in the S-F. β-d-Xylosidase activity increased by 99% in S-F from 2iP-treated callus but slightly decreased in the NaCl-F. In GA₃-treated callus, NaCl-F β-d-xylosidase activity increased by 188%. S-F and NaCl-F from Picloram-treated callus showed undetectable or only slightly noticeable α-l-arabinofuranosidase, α-d-xylosidase and β-d-xylosidase activity. Interestingly, β-d-glucosidase activity rose 28-fold in the S-F extracted from Picloram-treated callus. β-d-glucosidase was the only enzyme assayed that greatly increased its NaCl-F activity after 10 subcultures, and the addition of any PGR to the callus culture –except for Picloram and ABA– decreased its activity, suggesting that this enzyme may be associated with certain stress conditions, such as PGR starvation or Picloram addition. This is the first report on glycoside hydrolases from fruit callus as modulated by different PGRs.     

Activity levels of six glycoside hydrolases in apple fruit callus cultures depend on the type and concentration of carbohydrates supplied and the presence of plant growth regulators

Sucrose presence and concentration modulated in different ways and to different extents the activity of six plant glycoside hydrolases (PGHs) extracted from apple callus cultures, both in the water soluble fraction (WS-F) and in the NaCl-released fraction (NaCl-F). β-d-Glucosidase activity increased because of sucrose starvation and the addition of sucrose decreased both WS-F and NaCl-F β-d-glucosidase from calli grown in a Murashige and Skoog’s basal medium with (MSH) or without (MS0) plant growth regulators (PGRs). WS-F and NaCl-F α-l-arabinofuranosidase, NaCl-F β-d-galactosidase and NaCl-F β-d-xylosidase activity reached a maximum when 0.045 M sucrose was added to the MS0 medium with an ensuing decline at higher sucrose concentrations. α-d-Galactosidase and α-d-xylosidase activity reached a maximum when 0.045 M sucrose was supplied and did not decline significantly in 0.09 M sucrose-supplied calli. When the effects of PGR presence or absence were analysed, NaCl-F β-d-glucosidase, α-d-galactosidase, β-d-galactosidase, α-d-xylosidase and β-d-xylosidase activities were found to be higher in MS0 than in MSH. To assess whether sugar effects were sucrose-specific, other sugars (glucose, fructose, galactose, maltose, lactose, raffinose, sorbitol and mannitol) were tested, with or without PGR supplementation. In general, sugar alcohols (mannitol, sorbitol) and some monosaccharides (fructose and glucose in particular) were better inducers of NaCl-F α-l-arabinofuranosidase, β-d-galactosidase and β-d-xylosidase activity than disaccharides (sucrose, maltose, and lactose) or the trisaccharide raffinose. This trend was not widespread to all PGHs assessed since sucrose-supplemented calli displayed higher NaCl-F α-d-galactosidase than those supplemented with glucose, galactose, sorbitol or mannitol. These results show that sugars supplied to callus tissue cultures as a carbon source can also modulate PGH activity. Modulation is different for each PGH, sugar-specific and, at least in the case of sucrose, concentration-dependent. Results also suggest the existence of regulatory interactions between PGRs and sugars as part of an intricate sensing and signalling network. Combination of PGR, sugar type and concentration should be taken into account to maximize each PGH activity for further enzyme studies.     

Diffusivity of oxygen in aerobic granules

This work for the first time estimated apparent oxygen diffusivity (D(app)) of two types of aerobic granules, acetate-fed and phenol-fed, by probing the dissolved oxygen (DO) level at the granule center with a sudden change in the DO of the bulk liquid. With a high enough flow velocity across the granule to minimize the effects of external mass transfer resistance, the diffusivity coefficients of the two types of granules were estimated with reference to a one-dimensional diffusion model. The carbon source has a considerable effect on the granule diameter (d) and the oxygen diffusivity. The diffusivity coefficients were noted 1.24-2.28 x 10(-9) m2/s of 1.28-2.50 mm acetate-fed granules, and 2.50-7.65 x 10(-10) m2/s of 0.42-0.78 mm phenol-fed granules. Oxygen diffusivity declined with decreasing granule diameter, in particular, the diffusivity of acetate-fed granules is proportional to the size, whereas the diffusivity of phenol-fed granules is proportional to the square of granule diameter. The existence of large pores in granule, evidenced by FISH-CLSM imaging, was proposed to correspond to the noted size-dependent oxygen diffusivity. The phenol-fed granules exhibited a higher excellular polymer (ECP) content than the acetate-fed granules, hence yielding a lower oxygen diffusivity.     

Discovery of nigerose phosphorylase from Clostridium phytofermentans

A novel phosphorylase from Clostridium phytofermentans belonging to the glycoside hydrolase family (GH) 65 (Cphy1874) was characterized. The recombinant Cphy1874 protein produced in Escherichia coli showed phosphorolytic activity on nigerose in the presence of inorganic phosphate, resulting in the release of d-glucose and β-d-glucose 1-phosphate (β-G1P) with the inversion of the anomeric configuration. Kinetic parameters of the phosphorolytic activity on nigerose were k _cat = 67 s⁻¹ and K _m = 1.7 mM. This enzyme did not phosphorolyze substrates for the typical GH65 enzymes such as trehalose, maltose, and trehalose 6-phosphate except for a weak phosphorolytic activity on kojibiose. It showed the highest reverse phosphorolytic activity in the reverse reaction using d-glucose as the acceptor and β-G1P as the donor, and the product was mostly nigerose at the early stage of the reaction. The enzyme also showed reverse phosphorolytic activity, in a decreasing order, on d-xylose, 1,5-anhydro-d-glucitol, d-galactose, and methyl-α-d-glucoside. All major products were α-1,3-glucosyl disaccharides, although the reaction with d-xylose and methyl-α-d-glucoside produced significant amounts of α-1,2-glucosides as by-products. We propose 3-α-d-glucosyl-d-glucose:phosphate β-d-glucosyltransferase as the systematic name and nigerose phosphorylase as the short name for this Cphy1874 protein.     

Amylase activity in substrate deficiency aerobic granules

Immunohistochemical staining was applied together with the multicolor fluorescent scheme to demonstrate the amylase activity for polysaccharide hydrolysis in stored or starved aerobic granules that are in substrate deficiency. If sufficient nutrients were present, α-amylase and β-amylase were found close to the surface layer of the original granules. Following storage or starvation during which most external nutrients were depleted, the α-amylase and β-amylase were distributed over the entire granule interior, suggesting endogenous respiration at the core of the granule. In particular, the fluorescent intensities of α-amylase and β-amylase were enriched 5–20 μm from the edge of the internal cavity, suggesting the strong correlation between polysaccharide hydrolysis and the formation of interior cavities. The secreted amylase was located near the living cells, suggesting that the polysaccharide hydrolysis is restricted to local environment that occurs near the functional strains. Internal hydrolysis within the core, for the case of both proteins and polysaccharides should correspond in principle to the loss of granule stability.     

Synthesis of p-nitrophenyl sulfated disaccharides with beta-D-(6-sulfo)-GlcNAc units using beta-N-acetylhexosaminidase from Aspergillus oryzae in a transglycosylation reaction

When α-d-GlcNAc-OC₆H₄NO₂ -p and β-d-(6-sulfo)-GlcNAc-OC₆H₄NO₂-p (2) were used as substrates, β-N-acetylhexosaminidase from Aspergillus oryzae transferred the β-d-(6-sulfo)-GlcNAc(unit from 2 to α-d-GlcNAc-OC₆H₄NO₂ -p to afford β-d-(6-sulfo)-GlcNAc-(1→4)-α-d-GlcNAc-OC₆H₄NO₂-p (3) in a yield of 94% based on the amount of donor, 2, added. β-d-(6-sulfo)-GlcNAc-(1→4)-α-d-Glc-OC₆H₄NO₂-p (4) was obtained with α-d-Glc-OC₆H₄NO₂ -p as acceptor in a similar manner. With a reaction mixture of 2 and β-d-GlcNAc-OC₆H₄NO₂-p (1) in a molar ratio of 6:1, the enzyme mediated the transfer of β-d-GlcNAc from 1 to 2, affording disaccharide β-d-GlcNAc-(1→4)-β-(6-sulfo)-d-GlcNAc-OC₆H₄NO₂-p (5) in a yield of 13% based on the amount of 1 added.     

A comparison of enzymatic phosphorylation and phosphatidylation of β-l- and β-d-nucleosides

Enzymatic 5′-monophosphorylation and 5′-phosphatidylation of a number of β-l- and β-d-nucleosides was investigated. The first reaction, catalyzed by nucleoside phosphotransferase (NPT) from Erwinia herbicola, consisted of the transfer of the phosphate residue from p-nitrophenylphosphate (p-NPP) to the 5′-hydroxyl group of nucleoside; the second was the phospholipase d (PLD)-catalyzed transphosphatidylation of l-α-lecithin with a series of β-l- and β-d-nucleosides as the phosphatidyl acceptor resulted in the formation of the respective phospholipid-nucleoside conjugates. Some β-l-nucleosides displayed similar or even higher substrate activity compared to the β-d-enantiomers.     

Temporal and spatial appearance of wall polysaccharides during cellularization of barley (Hordeum vulgare) endosperm

Barley endosperm begins development as a syncytium where numerous nuclei line the perimeter of a large vacuolated central cell. Between 3 and 6 days after pollination (DAP) the multinucleate syncytium is cellularized by the centripetal synthesis of cell walls at the interfaces of nuclear cytoplasmic domains between individual nuclei. Here we report the temporal and spatial appearance of key polysaccharides in the cell walls of early developing endosperm of barley, prior to aleurone differentiation. Flowering spikes of barley plants grown under controlled glasshouse conditions were hand-pollinated and the developing grains collected from 3 to 8 DAP. Barley endosperm development was followed at the light and electron microscope levels with monoclonal antibodies specific for (1→3)-β-d-glucan (callose), (1→3,1→4)-β-d-glucan, hetero-(1→4)-β-d-mannans, arabino-(1→4)-β-d-xylans, arabinogalactan-proteins (AGPs) and with the enzyme, cellobiohydrolase II, to detect (1→4)-β-d-glucan (cellulose). Callose and cellulose were present in the first formed cell walls between 3 and 4 DAP. However, the presence of callose in the endosperm walls was transient and at 6 DAP was only detected in collars surrounding plasmodesmata. (1→3,1→4)-β-d-Glucan was not deposited in the developing cell walls until approximately 5 DAP and hetero-(1→4)-β-d-mannans followed at 6 DAP. Deposition of AGPs and arabinoxylan in the wall began at 7 and 8 DAP, respectively. For arabinoxylans, there is a possibility that they are deposited earlier in a highly substituted form that is inaccessible to the antibody. Arabinoxylan and heteromannan were also detected in Golgi and associated vesicles in the cytoplasm. In contrast, (1→3,1→4)-β-d-glucan was not detected in the cytoplasm in endosperm cells; similar results were obtained for coleoptile and suspension cultured cells.     

Characterization of a novel ginsenoside-hydrolyzing α-l-arabinofuranosidase, AbfA, from Rhodanobacter ginsenosidimutans Gsoil 3054T

The gene encoding an α-l-arabinofuranosidase that could biotransform ginsenoside Rc {3-O-[β-d-glucopyranosyl-(1–2)-β-d-glucopyranosyl]-20-O-[α-l-arabinofuranosyl-(1–6)-β-d-glucopyranosyl]-20(S)-protopanaxadiol} to ginsenoside Rd {3-O-[β-d-glucopyranosyl-(1–2)-β-d-glucopyranosyl]-20-O-β-d-glucopyranosyl-20(S)-protopanaxadiol} was cloned from a soil bacterium, Rhodanobacter ginsenosidimutans strain Gsoil 3054^T, and the recombinant enzyme was characterized. The enzyme (AbfA) hydrolyzed the arabinofuranosyl moiety from ginsenoside Rc and was classified as a family 51 glycoside hydrolase based on amino acid sequence analysis. Recombinant AbfA expressed in Escherichia coli hydrolyzed non-reducing arabinofuranoside moieties with apparent K _m values of 0.53 ± 0.07 and 0.30 ± 0.07 mM and V _max values of 27.1 ± 1.7 and 49.6 ± 4.1 μmol min⁻¹ mg⁻¹ of protein for p-nitrophenyl-α-l-arabinofuranoside and ginsenoside Rc, respectively. The enzyme exhibited preferential substrate specificity of the exo-type mode of action towards polyarabinosides or oligoarabinosides. AbfA demonstrated substrate-specific activity for the bioconversion of ginsenosides, as it hydrolyzed only arabinofuranoside moieties from ginsenoside Rc and its derivatives, and not other sugar groups. These results are the first report of a glycoside hydrolase family 51 α-l-arabinofuranosidase that can transform ginsenoside Rc to Rd.     

Site-directed mutagenesis of possible catalytic residues of cellobiose 2-epimerase from Ruminococcusalbus

The cellobiose 2-epimerase from Ruminococcus albus (RaCE) catalyzes the epimerization of cellobiose and lactose to 4-O-β-d-glucopyranosyl-d-mannose and 4-O-β-d-galactopyranosyl-d-mannose (epilactose). Based on the sequence alignment with N-acetyl-d-glucosamine 2-epimerases of known structure and on a homology-modeled structure of RaCE, we performed site-directed mutagenesis of possible catalytic residues in the enzyme, and the mutants were expressed in Escherichia coli cells. We found that R52, H243, E246, W249, W304, E308, and H374 were absolutely required for the activity of RaCE. F114 and W303 also contributed to catalysis. These residues protruded into the active-site cleft in the model (α/α)₆ core barrel structure.     

A review of acacic acid-type saponins from Leguminosae-Mimosoideae as potent cytotoxic and apoptosis inducing agents

The aim of this review is to highlight updated results on the biologically active saponins from Leguminosae-Mimosoideae. Acacic acid-type saponins (AATS), is a class of very complex glycosides possessing a common aglycon unit of the oleanane-type (acacic acid = 3β, 16α, 21β trihydroxy-olean-12-en-28 oic acid), having various oligosaccharide moieties at C-3 and C-28 and an acyl group at C-21. About sixty molecules of this type have been actively explored in recent years from Leguminosae family, from a chemical point of view and some fifty were reported to possess cancer related activities. These include cytotoxic/antitumor, immunomodulatory, antimutagenic, and apoptosis inducing properties and appear to depend on the acylation and esterification by different moieties at C-21 and C-28 of the acacic acid-type aglycone. One can observe that the (6S) configuration of the outer monoterpenyl moiety (MT) seems more potent in mediating high cytotoxicity than its (6R) isomer. Furthermore, the trisaccharide moiety {β-d-Xylopyranosyl-(1→2)-β-d-Fucopyranosyl-(1→6)- N-Acetamido 2-β-d-Glucopyranosyl-} at C-3, the tetrasaccharide moiety {β-d-Glucopyranosyl-(1→3)-[α-L-Arabinofuranosyl-(1→4)]-α-l-Rhamnopyranosyl-(1→2)-β-d-Glucopyranosyl} at C-28 of the aglycone, and the inner MT hydroxylated at its C-9, having a (6S) configuration can be important substituent patterns for the induction of apoptosis of AATS. Because of their interesting cytotoxic/apoptosis inducing activity, some AATS can be useful in the search for new potential antitumor agents from Fabaceae. Furthermore, the sequence 28-O-{Glc-(1→3)-[Ara_f-(1→4)]-Rha-(1→2)-Glc-Acacic acid}, often encountered in the genera Acacia, Albizia, Archidendron, and Pithecellobium may represent a chemotaxonomic marker of the Mimosoideae subfamily.     

Effect of light and reductones on differentiation of <Emphasis Type="Italic">Pleurotus ostreatus</Emphasis>

Vegetative mycelia of Pleurotus ostreatus were differentiated into primordia and subsequently into fruit bodies in synthetic sucrose-asparagine medium when exposed to light at low temperature. During photo-morphogenesis, l-ascorbic acid-like substances called reductones were produced. l-Ascorbic acid, d-eryth-roascorbic acid, 5-O-(α-d-glucopyranosyl)-d-erythroascorbic acid, 5-O-(α-d-xylopyranosyl)-d-erythroascorbic acid, 5-methyl-5-O-(α-d-glucopyranosyl)-d-erythroascorbic acid and 5-methyl-5-O-(α-d-xylopyranosyl)-d-eryth-roascorbic acid were accumulated initially in the illuminated mycelia before the initiation of fruiting. The content of glycosides of erythroascorbic acid and their methylated compounds increased again in the primordia and the fruit bodies. Exogenous L-ascorbic acid induced the formation of primordia from the mycelia in the dark in a dose-dependent manner. Thus, this suggests that these reductones might play a role in mediating the light stimulus in photomorphogenesis.     

Antigen 85C-mediated acyl-transfer between synthetic acyl donors and fragments of the arabinan

Antigen 85 (ag85) is a complex of acyltransferases (ag85A–C) known to play a role in the mycolation of the d-arabino-d-galactan (AG) component of the mycobacterial cell wall. In order to better understand the chemistry and substrate specificity of ag85, a trehalose monomycolate mimic p-nitrophenyl 6-O-octanoyl-β-d-glucopyranoside (1) containing an octanoyl moiety in lieu of a mycolyl moiety was synthesized as an acyl donor. Arabinofuranoside acceptors, methyl α-d-arabinofuranoside (2), methyl β-d-arabinofuranoside (3), and methyl 2-O-β-d-arabinofuranosyl-α-d-arabinofuranoside (9) were synthesized to mimic the terminal saccharides found on the AG. The acyl transfer reaction between acyl donor 1 and acceptors 2, 3, and 9 in the presence of ag85C from Mycobacterium tuberculosis (M. tuberculosis) resulted in the formation of esters, methyl 2, 5-di-O-octanoyl-α-d-arabinofuranoside (10), methyl 5-O-octanoyl-β-d-arabinofuranoside (11), and methyl 2-O-(5-O-octanoyl-β-d-arabinofuranosyl)-5-O-octanoyl-α-d-arabinofuranoside (12) in 2 h, 2 h and 8 h, respectively. The initial velocities of the reactions were determined with a newly developed assay for acyltransferases. As expected, the regioselectivity corresponds to mycolylation patterns found at the terminus of the AG in M. tuberculosis. The study shows that d-arabinose-based derivatives are capable of acting as substrates for ag85C-mediated acyl-transfer and the acyl glycoside 1 can be used in lieu of TMM extracted from bacteria to study ag85-mediated acyl-transfer and inhibition leading to the better understanding of the ag85 protein class. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The α-d-mannan core of a complex cell-wall heteroglycan of Trichoderma reesei is responsible for β-glucosidase activation

A heteroglycan responsible for the binding of the enzyme β-1,4-d-glucosidase (EC 3.2.1.21) to fungal cell walls was isolated from cell walls of the filamentous fungusTrichoderma reesei. The heteroglycan, composed of mannose, galactose, glucose, and glucuronic acid, also activated β-1,4-d-glucosidase, β-1,4-d-xylosidase andN-acetyl-β-1,4-d-glucosaminidase activity in vitro. The structural backbone of this heteroglycan was prepared by acid hydrolysis and gel filtration. The molecular structure of the core of the heteroglycan was determined by NMR studies as a linear α-1,6-d-mannan. The mannan core obtained by acid degradation stimulated the β-glucosidase activity by 90%. Several glycosidases fromAspergillus niger were also activated by theT. reesei heteroglycan. The β-glucosidase ofTrichoderma was activated by mannan fromSaccharomyces cerevisiae to a comparable extent.