The Action of Rice Branching Enzyme I (BEI) on Starches

The rice branching enzyme I (BEI) overproduced in Escherichia coli cells was investigated with respect to action on starches. BEI treatment decreased the turbidity of starch suspensions with distinct pasting behaviors from a native starch. This result suggests the great potential of BEI as a molecular tool for the production of a novel glucan polymer.     

ATPase activity in plasmalemma-rich vesicles isolated by aqueous two-phase partitioning from Vicia faba mesophyll and epidermis: Characterization and influence of abscisic acid and fusicoccin

Plasmalemma-rich microsomal vesicles were prepared from whole leaf and acid-washed epidermal tissue of Vicia faba L. cv. Osnabrücker Markt by aqueous two-phase partitioning in dextran T-500 and polyethylenglycol 1350 aqueous phases. These vesicles were tightly sealed and predominantly right-side out, and contained a K⁺ -stimulated, mg²⁺-dependent and vanadate-sensitive ATPase. The enzyme from both tissues exhibited nearly identical properties: pH optimum 6.4, K_m for ATP 0.60 mM(whole leaf) and 0.67 mM (epidermis). V_max -480 nmol (mg protein)¹ min¹ (whole leaf) and 510 nmol (mg protein)¹ min¹ (epidermis), I₅₀ (Na₃,VO₄) 7.5 μM (whole leaf) and 15 μM (epidermis). The enzyme was not inhibited by NO₃(50 mM)or sodium azide (I mM). DCCD (20 μM) reduced enzyme activity to 50% (whole leaf) and 58% (epidermis), gramicidin S (20 μM) to 36% (whole leaf) and 41%(epidermis). Ca²⁺ inhibited the ATPase [I₅₀, C²⁺: 0.5 mM(whole leaf) and 0.8 mM(epidermis)]. Ca²⁺ inhibited the ATPase [I₅₀, C²⁺ 0.5 mM(whole leaf) und 0.8 (epidermis)]. The vanadate-sensitive ATPase from whole leaf and epidermal tissue was slightly but significantly stimulated by fusicoccin (FC) at a concentration (0.13 μM) promoting stomatal opening. The stimulation was not seen in the solubilized ATPase. Stomata of the cultivar used here were insensitive lo (±)ABA up to 2 μM level which is effective in most other cultivars and species. Likewise, at this concentration no effect of ABA on the activity of the epidermal ATPase was observed. The data are discussed with respect to the interaction of FC and ABA with the ATPase.     

Cytotoxicity effect of algal polysaccharides on HL60 cells

The present study shows the cytotoxic effect of three different classes of algal polysaccharides on HL60 cells. Three galactofucans, fucoidan, and glucan were the polysaccharides utilized in this analysis. The parameters used for evaluating cell viability were [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) reduction, protein content, and phosphatase activity. We demonstrated stimulation of phosphatase activity, MTT reduction, and protein content in relation to three types of galactofucans (1, 2, and 3) with different molecular weights (1600, 1200, and 360 kD). However, when HL60 cells were treated with galactofucan type 3, the total protein remained unchanged. Under the same experimental conditions, an expressed increase in the phosphatase activity was detected when galactofucan 3 was utilized. In relation to the mitochondrial function, the stimulation was higher in cells treated with galactofucan type 1. Fucoidan did not have a significant effect on MTT reduction, but protein content was decreased (IC₅₀ around 30 μg/ml). Glucan also activated all the parameters that were analyzed, and this effect was more expressed in the phosphatase activity and in the protein content. This study provides new insights into the cytotoxic action of polysaccharides on HL60 cells and suggests for the first time the possible involvement of phosphatases in this process. Published in Russian in Biokhimiya, 2006, Vol. 71, No. 12, pp. 1613–1617.     

The LiCl effect on the conformation of lentinan in DMSO

Lentinan (β‐(1→3)‐D ‐glucan) was found to be successfully fractionated by the mixture of dimethyl sulfoxide (DMSO) and lithium chloride (LiCl) as a solvent and acetone as a precipitant. Light scattering and viscosity measurements were made on solutions of fractionated samples in pure DMSO and 0.2M LiCl/DMSO in the range of the molecular weight M_w from 21.7 × 10⁴ to 84.7 × 10⁴. The values of M_w in both solvents were almost the same, but the remarkable difference between the values of intrinsic viscosity [η] demonstrated that the LiCl/DMSO solvent greatly enhances the stiffness of the lentinan backbone. The observed intrinsic viscosity [η] was analyzed by the Yoshizaki‐Nitta‐Yamakawa theory of a worm‐like chain, and the persistence length q and molecular weight per unit contour length M_L were determined roughly as 6.0 nm and 890 g nm^?1 in 0.2M LiCl/DMSO, and 5.1 nm and 890 g nm^?1 in pure DMSO, respectively. This slightly larger persistent length in 0.2M LiCl/DMSO also confirmed the higher stiffness of lentinan enhanced by the LiCl/DMSO solvent. The enhancement of the chain stiffness was ascribed to the electrostatic repulsion because of the hydrogen bonding of the hydroxyl protons of lentinan with the chloride ion, which is in turn associated with the Li⁺(DMSO)_n macrocation complex. © 2012 Wiley Periodicals, Inc. Biopolymers 97: 840–845, 2012.     

An Arabidopsis callose synthase

-1,3-glucan polymers are major structural components of fungal cell walls, while cellulosic -1,4-glucan is the predominant polysaccharide in plant cell walls. Plant -1,3-glucan, called callose, is produced in pollen and in response to pathogen attack and wounding, but it has been unclear whether callose synthases can also produce cellulose and whether plant cellulose synthases may also produce -1,3-glucans. We describe here an Arabidopsis gene, AtGsl5, encoding a plasma membrane-localized protein homologous to yeast -1,3-glucan synthase whose expression partially complements a yeast -1,3-glucan synthase mutant. AtGsl5 is developmentally expressed at highest levels in flowers, consistent with flowers having high -1,3-glucan synthase activities for deposition of callose in pollen. A role for AtGsl5 in callose synthesis is also indicated by AtGsl5expression in the Arabidopsis mpk4 mutant which exhibits systemic acquired resistance (SAR), elevated -1,3-glucan synthase activity, and increased callose levels. In addition, AtGsl5 is a likely target of salicylic acid (SA)-dependent SAR, since AtGsl5mRNA accumulation is induced by SA in wild-type plants, while expression of the nahG salicylate hydroxylase reduces AtGsl5 mRNA levels in the mpk4 mutant. These results indicate that AtGsl5is likely involved in callose synthesis in flowering tissues and in the mpk4 mutant.     

Multiplicity of soluble glucan-synthase activity in spinach leaves: Enzyme pattern and intracellular location

Buffer-extractable proteins from leaves of Spinacia oleracea L. were separated by non-denaturing polyacrylamide gel electrophoresis. Gels were stained for adenosine diphosphoglucose (ADPglucose)-dependent glucan-synthase (GS) activity (EC 2.4.1.21). Three major forms of activity were observed. No staining was detectable when ADPglucose was replaced by an equimolar concentration of either uridine, guanosine or cytosine diphosphoglucose. Two of the three GS forms exhibited both primed and citrate-stimulated unprimed activity whereas one enzyme form was strictly dependent upon the presence of an exogenous glucan. For intracellular localization, mesophyll protoplasts and intact chloroplasts were isolated and their enzyme pattern was compared with that of the leaf extract. Intactness and purity of the chloroplast preparations were ascertained by polarographic measurement of the ferricyanide- or CO₂-dependent oxygen evolution, by determination of marker-enzyme activities, and by electrophoretic evaluation of the content of chloroplast- and cytosol-specific glucanphosphorylase forms (EC 2.4.1.1). The three GS forms were present in mesophyll protoplasts. Intact chloroplasts possessed both primer-independent enzyme forms but lacked the primer-dependent one. The latter form was enriched in supernatant fractions of leaf homogenates when the intact chloroplasts had been pelleted by centrifugation. Thus, in spinach-leaf mesophyll cells soluble ADPglucose-dependent GS is located both inside and outside the chloroplast.Abbreviations GS glucan synthase - PAGE polyacrylamide gel electrophoresis This work has been made possible by grants from the Deutsche Forschungsgemeinschaft and from the Minister für Wissenschaft und Forschung des Landes Nordrhein-Westfalen. The authors gratefully acknowledge the generous permission to use the laser densitometer of Professor Dr. W. Barz (Biochemie der Pflanzen, Universität Münster, FRG). They are indebted to Dr. H.-J. Witt (Pflanzenphysiologie, Universität Kassel, FRG) for helpful discussions and to Mr. W. Lamkemeyer for skilfull technical assistance.     

Interaction investigations of crustacean β‐GBP recognition toward pathogenic microbial cell membrane and stimulate upon prophenoloxidase activation

In invertebrates, crustaceans' immune system consists of pattern recognition receptors (PRRs) instead of immunoglobulin's, which involves in the microbial recognition and initiates the protein–ligand interaction between hosts and pathogens. In the present study, PRRs namely β‐1,3 glucan binding protein (β‐GBP) from mangrove crab Episesarma tetragonum and its interactions with the pathogens such as bacterial and fungal outer membrane proteins (OMP) were investigated through microbial aggregation and computational interaction studies. Molecular recognition and microbial aggregation results of Episesarma tetragonum β‐GBP showed the specific binding affinity toward the fungal β‐1,3 glucan molecule when compared to other bacterial ligands. Because of this microbial recognition, prophenoloxidase activity was enhanced and triggers the innate immunity inside the host animal. Our findings disclose the role of β‐GBP in molecular recognition, host–pathogen interaction through microbial aggregation, and docking analysis. In vitro results were concurred with the in silico docking, and molecular dynamics simulation analysis. This study would be helpful to understand the molecular mechanism of β‐GBP and update the current knowledge on the PRRs of crustaceans. Copyright © 2014 John Wiley & Sons, Ltd.     

Crystal structure at 1.45-A resolution of the major allergen endo-beta-1,3-glucanase of banana as a molecular basis for the latex-fruit syndrome

Resolution of the crystal structure of the banana fruit endo-beta-1,3-glucanase by synchrotron X-ray diffraction at 1.45-A resolution revealed that the enzyme possesses the eightfold beta/alpha architecture typical for family 17 glycoside hydrolases. The electronegatively charged catalytic central cleft harbors the two glutamate residues (Glu94 and Glu236) acting as hydrogen donor and nucleophile residue, respectively. Modeling using a beta-1,3 linked glucan trisaccharide as a substrate confirmed that the enzyme readily accommodates a beta-1,3-glycosidic linkage in the slightly curved catalytic groove between the glucose units in positions -2 and -1 because of the particular orientation of residue Tyr33 delimiting subsite -2. The location of Phe177 in the proximity of subsite +1 suggested that the banana glucanase might also cleave beta-1,6-branched glucans. Enzymatic assays using pustulan as a substrate demonstrated that the banana glucanase can also cleave beta-1,6-glucans as was predicted from docking experiments. Similar to many other plant endo-beta-1,3-glucanases, the banana glucanase exhibits allergenic properties because of the occurrence of well-conserved IgE-binding epitopes on the surface of the enzyme. These epitopes might trigger some cross-reactions toward IgE antibodies and thus account for the IgE-binding cross-reactivity frequently reported in patients with the latex-fruit syndrome.     

β-1-4-and β-1-3-glucan synthases are associated with the plasma membrane of the fungus Saprolegnia

Cytoplasmic membranes from mycelium or protoplasts of Saprolegnia monoica (a cellulosic cell-wall fungus) were separated by continuous sucrose-density-gradient centrifugation. Glucan synthases assayed at low (micromolar uridine 5-diphosphate (UDP) glucose for -1-4-glucan synthase) and high (millimolar UDP glucose for -1-3-glucan synthase) substrate concentrations were associated with membranes exhibiting vanadate-sensitive, oligomycin-insensitive ATPase and equilibrating at density 1.16 g cm^-3. Synthase activities were also bound to membranes of lower density (1.10 and 1.145 g cm^-3). Plasma membranes were stabilized by coating protoplasts with concanavalin A. After lysis of the protoplasts, plasma membranes recovered by low centrifugal forces were isolated in continuous isopycinic gradients. Both synthase activities peaked with [³H]concanavalin A and Na-vanadate ATPase indicating that the synthetases are located at the plasma membrane. Treatments of intact protoplasts with cold glutaraldehyde or proteases before disruption lead to a diminution of glucan-synthase activities indicating that at least part of the enzymes of plasma membrane face the outside of the cell.Abbreviations ConA concanavalin A - ER endoplasmic reticulum - GSI -1,4-glucan synthase - GSH -1,3-glucan synthase - UDP uridine 5-diphosphate