Amount Of Glucan Research Articles

Mechanism of synthesis of d-glucans by d-glucosyltransferases from Streptococcus mutans 6715

Two glucosyltransferases from Streptococcus mutans 6715 were purified and separated. One of the glucosyltransferases synthesized an insoluble glucan, and the other, a soluble glucan. The enzymes were immobilized on Bio-Gel P-2 beads, and the mechanism of glucan synthesis was studied by pulse and chase techniques with 14C-sucrose. Label was associated with the immobilized enzymes. The label could be quantitatively released by heating at pH 2. Analysis of the labeled products from the pulse experiment showed labeled glucose and labeled glucan; the chase experiment showed labeled glucan and a significant decrease in labeled glucose. The glucans from the pulse and the chase experiments were separated from glucose by chromatography on Bio-Gel P-6. They were reduced with sodium borohydride, and the products hydrolyzed with acid. Analysis of the labeled products from the reduced and hydrolyzed, pulsed glucans showed labeled glucose and labeled glucitol; label in the glucitol was greatly decreased in the chase experiment. These experiments showed that glucose and glucan were covalently attached to the active site of the enzymes during synthesis, and that the glucose was being transferred to the reducing end of the glucan chain. A mechanism for the synthesis of the glucans is proposed in which there are two catalytic groups on each enzyme that holds glucosyl and glucanosyl units. During synthesis, the glucosyl and glucanosyl units alternate between the two sites, giving elongation of the glucans from the reducing end. The addition of increasing amounts of B-512F dextran to the insoluble-glucan-forming glucosyltransferase produced a decrease in the proportion of insoluble glucan formed and a concomitant increase in a soluble glucan. The total amount of glucan synthesized (soluble plus insoluble) was increased 1.6 times over the amount of insoluble glucan formed when no exogenous dextran was added. It is shown that the addition of B-512F dextran affects the solubility of the synthesized α-(1→3)-glucan by accepting α-(1→3)-glucan chains at various positions along the dextran chain, to give a soluble, graft polymer.

Directly compressed tablets containing water-insoluble glucan and microcrystalline cellulose in addition to lactose.

In order to investigate the pharmaceutical availability of the water-insoluble glucan produced by Streptococcus mutans, application of the glucan as a filler for directly compressed tablets was studied. The fluidity of combined powder of glucan with lactose was determined and then the hardness and the disintegration properties of directly compressed tablets of these mixtures were studied in comparison with those of tablets containing microcrystalline cellulose (MCC). The fluidity of the powder mixture was not much improved by the addition of glucan to lactose. The hardness of tablets containing glucan was higher than that of tablets containing MCC over the concentration range used in this experiment (4-50%). However, the disintegration properties of tablets containing a large amount of glucan were inferior to those of tablets containing the same amount of MCC, as the disintegration took place immediately when the concentration of glucan was lower than 20% but was retarded gradually at glucan levels higher than 25%. The hardness of tablets containing glucan increased with increase in the compressional pressure, but the disintegration properties were not changed. Further, in the dissolution study of ascorbic acid (V.C.) from the tablets, immediate dissolution of V.C. was obtained and no inhibition of dissolution of V.C. by glucan was observed. Overall, these results suggest that the water-insoluble glucan may be practically useful as a filler for directly compressed tablets.

Effects of exogenous insoluble glucan primer on insoluble glucan synthesis by Streptococcus mutans.

The effects of exogenous glucans on WIG synthesis by S. mutans were investigated by turbidimetric measurement. The rapid synthesis of WIG by an enzyme preparation from PS-14 culture fluid proceeded after a lag period of several min. The addition of exogenous WIG, which was previously prepared using the PS-14 enzyme, caused a marked reduction of the lag period with little change in the reaction rate. The length of lag period was affected by the concentrations of WIG primer, enzyme and salts, and the reaction pH. The WIGs from other strains and the periodate-treated WIGs also exhibited effects similar to the PS-14 glucan. In contrast, dextran, starch, dextrin, laminarin, cellulose, chitin, and inulin were without any effect. These results suggest that such lag-reducing effect is specific to glucans containing a significant amount of alpha-(1 leads to 3) linkages.

The Relationship Between the Uptake of Glucose and 3-O-Methylglucose and Soluble Carbohydrate and Polysaccharide in the Fungus Dendryphiella salina

When mycelium of Dendryphiella salina, pre-incubated in D-[I-14C]mannitol such that this is the only major labelled soluble carbohydrate present, absorbs glucose or the non-metabolized sugar 3-O-methylglucose, there is a specific stimulation of incorporation of 14C into alkali-insoluble, trichloroacetic-acid-soluble (1 leads to 4)-alpha-glucan, probably glycogen. There is also a net increase in the amount of glucan caused by stimulation of synthesis and inhibition of breakdown. Addition of 3-O-methylglucose results in the loss of mannitol into the medium. This loss and the reduced rate of replenishment from the glucan is important in the osmotic regulation of the hyphae. If osmotic adjustment does not occur, the hyphae do not show the specific incorporation of 14C into the glucan.

Macrophage-Mediated Destruction of Human Malignant Cells In Vivo<xref ref-type="fn" rid="fn2">2</xref>

Macrophages require a plasma component, designated "recognition factor" (RF), for the expression of optimal function. The RF activity was profoundly depleted in plasma from patients with malignant disease, and the degree of depletion and the severity of the malignant state seemed to be related. Since experiments demonstrated that an active RF significantly inhibited tumor growth, clinical studies were initiated to investigate the influence of intratumor administration of an active RF fraction. Glucan, a potent macrophage activator, was also employed alone or combined with RF. These studies were undertaken to enhance the recognition of malignant cells by macrophages and to mobilize and activate macrophages intralesionally. The initial 9 patients studied had malignant melanoma, adenosquamous carcinoma of the lung, or carcinoma of the breast. Control and experimental lesions were injected; subsequently biopsies were performed at varying intervals for histologic evaluation. Always when glucan or glucan and RF fraction were administered intralesionally, the size of the lesion was strikingly reduced in as short a period as 5 days. This reduction was associated with necrosis of the tumor and a monocytic infiltrate. In small lesions, resolution was complete, whereas in large lesions, resolution was partial. The amount of glucan injected and the quantity of residual tumor appeared to be related. The induced necrosis of the tumor nodule was associated with an increase in plasma levels of circulating RF activity.

CHANGE OF CELL WALL POLYSACCHARIDES OF YEAST IN BIOTIN DEFICIENCY

1. In biotin deficient yeast, thickening of cell wall was conspicuous at the middle log phase in the Am medium, whereas it was not in the aged cells. The cells cultivated in the Cas medium do not have thickened cell wall even in biotin deficiency. The ratio of mannan to glucan also decreased in the Cas medium, as well as in the Am medium, but, in pantothenic acid deficiency, the ratio did not decrease. In general, total amounts of glucan and mannan showed good parallelism with the thickness of cell wall observed in electron microscopy.2. Investigations were made on the change of mannan and glucan of yeast at the process of the dead cell formation which appeared in the biotin- free aspartic acid medium and the results showed that mannan tended to increase.

SYNTHESIS OF CELL WALL POLYSACCHARIDES IN THE CELL CYCLE OF BAKER'S YEAST

Cell wall polysaccharide content of small- and large-sized cells which were obtained by fractional centrifugation of commercial baker's yeast was determined. The small-sized cells contained significantly lower amount of glucan and higher amount of mannan than the large-sized cells. Glucan content of small cells obtained by the fractionation of laboratory-cultured cells was also lower than original cells, and increased by various treatments which make the cell size larger. Determination of cell wall polysaccharides during the course of synchronous proliferation of large cells revealed that mannan is synthesized linearly during cell division cycles, whereas glucan synthesis proceeded intermittently; that is, it was seen mainly in the latter half of the cell division cycle. The difference in cell wall polysaccharide content between the small and large cells might be explained from these results and the position of the small cells in the cell division cycle, which was discussed in the preceding paper.

Formation and structure of extracellular glucans produced by Claviceps species.

SUMMARY: Submerged cultures of Claviceps fusiformis (Loveless) became progressively viscous during the incubation because of the production of an extracellular polysaccharide. The polysaccharide was shown to be a branched glucan with a β1 → 3 linked main chain having single glucopyranosyl units at intervals along it in the β1 → 6 configuration. For most of the media investigated growth at 27° and between pH 5 and 6 was accompanied by glucan production, which ceased when growth was arrested by lack of nutrient. The glucan was re-metabolized by the fungus only to a limited extent as the culture aged; the degree of branching varied during the culture period. The unit amount of glucan synthesized was not affected by numerous successive subculturings over a period of several months, but the product from the later cultures had a greater degree of branching. Branched glucans of similar structure to the above were also detected in low concentration in the natural sclerotia. The presence of β1 → 3 linked glucans in the cell walls of this and other fungal strains examined was also indicated.

Morphometric analysis of yeast cells: II. Cell size of Schizosaccharomyces pombe during the growth cycle

The growth cycle of cultures of Schizosaccharomyces pombe is characterized by the usual lag, log and stationary phases. The mean cell size of the population of yeast cells changes in a consistent manner through the growth cycle. When cultures are inoculated with stationary cells, there is through the lag phase a predominantly exponential rate of cellular extension. This observation constitutes further evidence suggesting that the extension of S. pombe ordinarily increases exponentially through the cell cycle. The mean cell size is greatest at the transition between the lag and log phases. In fact the range is displaced, as immature cells through most of the log phase are larger than immature cells at the beginning of the stationary phase. The mean cell size decreases exponentially through the log phase, and the amount of glucan per cell changes proportionally with the decrease in cell size. In addition, the cell-plate index falls constantly through the log phase, presumbly indicating that the cell cycle itself changes through the log phase. All of these observations indicate the unbalanced nature of growth of this yeast in culture. These and similar observations (by others) on a large number of other microorganisms suggest that unbalanced growth is a common phenomenon.

Composition of cells and cell walls of triangular and ellipsoidal forms of Trigonopsis variabilis.

SUMMARY: Extraction and fractionation of lipids from intact ellipsoidal and triangular forms of Trigonopsis variabilis showed both to be rich in lipid, the content in triangular forms being twice that in ellipsoidal forms. Lipid was chiefly present in bound form with which principally choline was associated in triangular cells, whilst in ellipsoidal cells ethanolamine and serine predominated. Very little unsaturated lipid was found in the triangular forms, whereas a threefold greater iodine value was noted with the ellipsoidal forms. Polysaccharides of both cellular forms were extracted and fractionated. The triangular forms were seemingly devoid of glucan or chitin but contained a reducing polysaccharide that formed an unusual copper complex and appeared to be a polymer of glucose and mannose. The ellipsoidal forms contained a small amount of glucan and considerable amounts of glycogen. Cell walls were isolated from both triangular and ellipsoidal forms and found to consist principally of polysaccharide, nearly all of which was alkali-soluble. Walls of triangular forms contained somewhat more lipid than those of ellipsoidal forms, and phospholipid was twice that of ellipsoidal form walls.

ON THE POLYSACCARIDES EXTRACTED FROM PULPS BY BEATING

In determination of alkali solubilities of beaten birch bleached sulphite pulp (see Fig. 1 and 2), it has been found that the 10% NaOH solubility tends to increase with the progrese of beating, but the 0.5, 1, 5 and 18% NaOH solubilities tend to decrease (see Fig. 3). The amount of glucan in 10% HaOH soluble substances increass by beating, while the amount of xylan, mannan and uronic residues remains nearly constant (see Table 1).By analysis of soluble substance extracted by beating, it is found that methylglucuronoxylan is extracted from the pulp by beating (see Table 2).In the case of beating of birch holocellulose, small amount of polysaccharides composed of rhamnose-, arabinose-, galactose-, mannose- and glucose-residues are extracted in addition to methylglucuronoxylan (see Table 4). Xylan extracted from the pulp and holocellulose is very rich in uronic acid, and the ratio of uronic units to xylose is 1:13 and 1:7-9, respectively., whereas the ratio in the xylan of birch bleached sulphite pulp and holocellulose 1:23 and 1:12, respectively, (see Table 3).Although fir (Abies Mayriana) bleached sulphite pulp contains larger amount of glucomannan (see Table 5), only methylglucuronoxylan is extracted from the pulp by beating (see Table 6).