Simulated digestions of free oligosaccharides and mucin-type O-glycans reveal a potential role for Clostridium perfringens

The development of a stable human gut microbiota occurs within the first year of life. Many open questions remain about how microfloral species are influenced by the composition of milk, in particular its content of human milk oligosaccharides (HMOs). The objective is to investigate the effect of the human HMO glycome on bacterial symbiosis and competition, based on the glycoside hydrolase (GH) enzyme activities known to be present in microbial species. We extracted from UniProt a list of all bacterial species catalysing glycoside hydrolase activities (EC 3.2.1.-), cross-referencing with the BRENDA database, and obtained a set of taxonomic lineages and CAZy family data. A set of 13 documented enzyme activities was selected and modelled within an enzyme simulator according to a method described previously in the context of biosynthesis. A diverse population of experimentally observed HMOs was fed to the simulator, and the enzymes matching specific bacterial species were recorded, based on their appearance of individual enzymes in the UniProt dataset. Pairs of bacterial species were identified that possessed complementary enzyme profiles enabling the digestion of the HMO glycome, from which potential symbioses could be inferred. Conversely, bacterial species having similar GH enzyme profiles were considered likely to be in competition for the same set of dietary HMOs within the gut of the newborn. We generated a set of putative biodegradative networks from the simulator output, which provides a visualisation of the ability of organisms to digest HMO and mucin-type O-glycans. B. bifidum, B. longum and C. perfringens species were predicted to have the most diverse GH activity and therefore to excel in their ability to digest these substrates. The expected cooperative role of Bifidobacteriales contrasts with the surprising capacities of the pathogen. These findings indicate that potential pathogens may associate in human gut based on their shared glycoside hydrolase digestive apparatus, and which, in the event of colonisation, might result in dysbiosis. The methods described can readily be adapted to other enzyme categories and species as well as being easily fine-tuneable if new degrading enzymes are identified and require inclusion in the model.

Characterization of an antifungal β-1,3-glucanase from Ficus microcarpa latex and comparison of plant and bacterial β-1,3-glucanases for fungal cell wall β-glucan degradation

MAIN CONCLUSION

Each β-1,3-glucanase with antifungal activity or yeast lytic activity hydrolyzes different structures of β-1,3-glucans in the fungal cell wall, respectively. Plants express several glycoside hydrolases that target chitin and β-glucan in fungal cell walls and inhibit pathogenic fungal infection. An antifungal β-1,3-glucanase was purified from gazyumaru (Ficus microcarpa) latex, designated as GlxGluA, and the corresponding gene was cloned and expressed in Escherichia coli. The sequence shows that GlxGluA belongs to glycoside hydrolase family 17 (GH17). To investigate how GlxGluA acts to degrade fungal cell wall β-glucan, it was compared with β-1,3-glucanase with different substrate specificities. We obtained recombinant β-1,3-glucanase (designated as CcGluA), which belongs to GH64, from the bacterium Cellulosimicrobium cellulans. GlxGluA inhibited the growth of the filamentous fungus Trichoderma viride but was unable to lyse the yeast Saccharomyces cerevisiae. In contrast, CcGluA lysed yeast cells but had a negligible inhibitory effect on the growth of filamentous fungi. GlxGluA degraded the cell wall of T. viride better than CcGluA, whereas CcGluA degraded the cell wall of S. cerevisiae more efficiently than GlxGluA. These results suggest that the target substrates in fungal cell walls differ between GlxGluA (GH17 class I β-1,3-glucanase) and CcGluA (GH64 β-1,3-glucanase).

3D-printed microfluidics integrated with optical nanostructured porous aptasensors for protein detection

Microfluidic integration of biosensors enables improved biosensing performance and sophisticated lab-on-a-chip platform design for numerous applications. While soft lithography and polydimethylsiloxane (PDMS)-based microfluidics are still considered the gold standard, 3D-printing has emerged as a promising fabrication alternative for microfluidic systems. Herein, a 3D-printed polyacrylate-based microfluidic platform is integrated for the first time with a label-free porous silicon (PSi)-based optical aptasensor via a facile bonding method. The latter utilizes a UV-curable adhesive as an intermediate layer, while preserving the delicate nanostructure of the porous regions within the microchannels. As a proof-of-concept, a generic model aptasensor for label-free detection of his-tagged proteins is constructed, characterized, and compared to non-microfluidic and PDMS-based microfluidic setups. Detection of the target protein is carried out by real-time monitoring reflectivity changes of the PSi, induced by the target binding to the immobilized aptamers within the porous nanostructure. The microfluidic integrated aptasensor has been successfully used for detection of a model target protein, in the range 0.25 to 18 μM, with a good selectivity and an improved limit of detection, when compared to a non-microfluidic biosensing platform (0.04 μM vs. 2.7 μM, respectively). Furthermore, a superior performance of the 3D-printed microfluidic aptasensor is obtained, compared to a conventional PDMS-based microfluidic platform with similar dimensions.

Dissipation of chlorantraniliprole in contrasting soils and its effect on soil microbes and enzymes

An experiment was set up to determine the rate of dissipation of chlorantraniliprole (CTP) from two soils with contrasting properties. The other objective of the study was to find out the effect of CTP on soil microorganisms (population, microbial biomass carbon and soil enzymes) under controlled environment. CTP residues when applied at recommended dose ((RD) (at 40 g a.i./ha)) could not be recovered either from alluvial soil or red soil at 60 days post application of CTP in a microcosm study. Higher clay content led to higher half-life in alluvial soil compared to red soil. CTP could not be recovered from RD treatment at 30 days after pesticide application under controlled environment. Faster dissipation of CTP was observed in rice rhizosphere soil with 23.89 and 34.65 days dissipation half-lives for RD and double the recommended dose (DRD) treatments, respectively. Different doses of chlorantraniliprole did not have considerable negative effect on actinomycetes, fungi, biological nitrogen fixers and phospahte solubilising bacteria except the bacteria population. Among the treatments, DRD recorded the lowest activity of dehyrodeganse, fluoresein diacetate hydrolase, acid and alkaline phosphatases followed by RD treatment. Microbial biomass carbon, β -glycosidase and urease did not vary significantly among the different doses of CTP. In general, RD did not have negative effcts on soil microbes. Hence, CTP can be recommeded in rice pest managment maintaining existing soil microbes and soil enzymes activity.

Monitoring Poly(ADP-ribosyl)glycohydrolase Activity with a Continuous Fluorescent Substrate

The post-translational modification (PTM) and signaling molecule poly(ADP-ribose) (PAR) has an impact on diverse biological processes. This PTM is regulated by a series of ADP-ribosyl glycohydrolases (PARG enzymes) that cleave polymers and/or liberate monomers from their protein targets. Existing methods for monitoring these hydrolases rely on detection of the natural substrate, PAR, commonly achieved via radioisotopic labeling. Here we disclose a general substrate for monitoring PARG activity, TFMU-ADPr, which directly reports on total PAR hydrolase activity via release of a fluorophore; this substrate has excellent reactivity, generality (processed by the major PARG enzymes), stability, and usability. A second substrate, TFMU-IDPr, selectively reports on PARG activity only from the enzyme ARH3. Use of these probes in whole-cell lysate experiments has revealed a mechanism by which ARH3 is inhibited by cholera toxin. TFMU-ADPr and TFMU-IDPr are versatile tools for assessing small-molecule inhibitors in vitro and probing the regulation of ADP-ribosyl catabolic enzymes.

Diversity of Microbial Carbohydrate-Active enZYmes (CAZYmes) Associated with Freshwater and Soil Samples from Caatinga Biome

Semi-arid and arid areas occupy about 33% of terrestrial ecosystems. However, little information is available about microbial diversity in the semi-arid Caatinga, which represents a unique biome that extends to about 11% of the Brazilian territory and is home to extraordinary diversity and high endemism level of species. In this study, we characterized the diversity of microbial genes associated with biomass conversion (carbohydrate-active enzymes, or so-called CAZYmes) in soil and freshwater of the Caatinga. Our results showed distinct CAZYme profiles in the soil and freshwater samples. Glycoside hydrolases and glycosyltransferases were the most abundant CAZYme families, with glycoside hydrolases more dominant in soil (∼44%) and glycosyltransferases more abundant in freshwater (∼50%). The abundances of individual glycoside hydrolase, glycosyltransferase, and carbohydrate-binding module subfamilies varied widely between soil and water samples. A predominance of glycoside hydrolases was observed in soil, and a higher contribution of enzymes involved in carbohydrate biosynthesis was observed in freshwater. The main taxa associated with the CAZYme sequences were Planctomycetia (relative abundance in soil, 29%) and Alphaproteobacteria (relative abundance in freshwater, 27%). Approximately 5-7% of CAZYme sequences showed low similarity with sequences deposited in non-redundant databases, suggesting putative homologues. Our findings represent a first attempt to describe specific microbial CAZYme profiles for environmental samples. Characterizing these enzyme groups associated with the conversion of carbohydrates in nature will improve our understanding of the significant roles of enzymes in the carbon cycle. We identified a CAZYme signature that can be used to discriminate between soil and freshwater samples, and this signature may be related to the microbial species adapted to the habitat. The data show the potential ecological roles of the CAZYme repertoire and associated biotechnological applications.

Comparative secretomic analysis of lignocellulose degradation by Lentinula edodes grown on microcrystalline cellulose, lignosulfonate and glucose

Lentinula edodes has the potential to degrade woody and nonwoody lignocellulosic biomass. However, the mechanism of lignocellulose degradation by L. edodes is unclear. The aim of this work is to explore the profiling of soluble secreted proteins involved in lignocellulose degradation in L. edodes. For that, we compared the secretomes of L. edodes grown on microcrystalline cellulose, cellulose with lignosulfonate and glucose. Based on nanoliquid chromatography coupled with tandem mass spectrometry of whole-protein hydrolysate, 230 proteins were identified. Label-free proteomic analysis showed that the most abundant carbohydrate-active enzymes involved in polysaccharide hydrolysis were endo-β-1,4-glucanase, α-galactosidase, polygalacturonase and glucoamylase in both cellulosic secretomes. In contrast, enzymes involved in lignin degradation were most abundant in glucose culture, with laccase 1 being the predominant protein (13.13%). When the cellulose and cellulose with lignosulfonate secretomes were compared, the abundance of cellulases and hemicellulases was higher in cellulose with lignosulfonate cultures, which was confirmed by enzyme activity assays. In addition, qRT-PCR analysis demonstrated that the expression levels of genes encoding cellulases and hemicellulases were significantly increased (by 32.2- to 1166.7-fold) when L. edodes was grown in cellulose with lignosulfonate medium.

BIOLOGICAL SIGNIFICANCE

In this article, the secretomes of L. edodes grown on three different carbon sources were compared. The presented results revealed the profiling of extracellular enzymes involved in lignocellulose degradation, which is helpful to further explore the mechanism of biomass bioconversion by L. edodes.

A proteomic analysis of Pakistan Daboia russelii russelii venom and assessment of potency of Indian polyvalent and monovalent antivenom

To address the dearth of knowledge on the biochemical composition of Pakistan Russell's Viper (Daboia russelii russelii) venom (RVV), the venom proteome has been analyzed and several biochemical and pharmacological properties of the venom were investigated. SDS-PAGE (reduced) analysis indicated that proteins/peptides in the molecular mass range of ~56.0-105.0kDa, 31.6-51.0kDa, 15.6-30.0kDa, 9.0-14.2kDa and 5.6-7.2kDa contribute approximately 9.8%, 12.1%, 13.4%, 34.1% and 30.5%, respectively of Pakistan RVV. Proteomics analysis of gel-filtration peaks of RVV resulted in identification of 75 proteins/peptides which belong to 14 distinct snake venom protein families. Phospholipases A2 (32.8%), Kunitz type serine protease inhibitors (28.4%), and snake venom metalloproteases (21.8%) comprised the majority of Pakistan RVV proteins, while 11 additional families accounted for 6.5-0.2%. Occurrence of aminotransferase, endo-β-glycosidase, and disintegrins is reported for the first time in RVV. Several of RVV proteins/peptides share significant sequence homology across Viperidae subfamilies. Pakistan RVV was well recognized by both the polyvalent (PAV) and monovalent (MAV) antivenom manufactured in India; nonetheless, immunological cross-reactivity determined by ELISA and neutralization of pro-coagulant/anticoagulant activity of RVV and its fractions by MAV surpassed that of PAV.

BIOLOGICAL SIGNIFICANCE

The study establishes the proteome profile of the Pakistan RVV, thereby indicating the presence of diverse proteins and peptides that play a significant role in the pathophysiology of RVV bite. Further, the proteomic findings will contribute to understand the variation in venom composition owing to different geographical location and identification of pharmacologically important proteins in Pakistan RVV.

A high-throughput screening-compatible homogeneous time-resolved fluorescence assay measuring the glycohydrolase activity of human poly(ADP-ribose) glycohydrolase

Poly(ADP-ribose) (PAR) polymers are transient post-translational modifications, and their formation is catalyzed by poly(ADP-ribose) polymerase (PARP) enzymes. A number of PARP inhibitors are in advanced clinical development for BRCA-mutated breast cancer, and olaparib has recently been approved for BRCA-mutant ovarian cancer; however, there has already been evidence of developed resistance mechanisms. Poly(ADP-ribose) glycohydrolase (PARG) catalyzes the hydrolysis of the endo- and exo-glycosidic bonds within the PAR polymers. As an alternative strategy, PARG is a potentially attractive therapeutic target. There is only one PARG gene, compared with 17 known PARP family members, and therefore a PARG inhibitor may have wider application with fewer compensatory mechanisms. Prior to the initiation of this project, there were no known existing cell-permeable small molecule PARG inhibitors for use as tool compounds to assess these hypotheses and no suitable high-throughput screening (HTS)-compatible biochemical assays available to identify start points for a drug discovery project. The development of this newly described high-throughput homogeneous time-resolved fluorescence (HTRF) assay has allowed HTS to proceed and, from this, the identification and advancement of multiple validated series of tool compounds for PARG inhibition.

Enzymes enhance degradation of the fiber-starch-protein matrix of distillers dried grains with solubles as revealed by a porcine in vitro fermentation model and microscopy

Effects of treating corn and wheat distillers dried grains with solubles (DDGS) with a multicarbohydrase alone or in combination with a protease on porcine in vitro fermentation characteristics and the matrix structure of the DGGS before and after the fermentation were studied. Three DDGS samples (wheat DDGS sample 1 [wDDGS1], wheat DDGS sample 2 [wDDGS2], and corn DDGS [cDDGS]) were predigested with pepsin and pancreatin. Residues were then subjected to in vitro fermentation using buffered mineral solution inoculated with fresh pig feces without or with a multicarbohydrase alone or in combination with protease in a 3 × 3 factorial arrangement. Accumulated gas production was measured for up to 72 h. Concentration of VFA was measured in fermented solutions. The matrix of native DDGS and their residues after fermentation was analyzed using confocal laser scanning microscopy and scanning electron microscopy to determine internal and external structures, respectively. On a DM basis, wDDGS1, wDDGS2, and cDDGS contained 35.5, 43.4, and 29.0% CP; 2.23, 0.51, and 6.40% starch; 0.82, 0.80, and 0.89% available Lys; and 24.8, 22.5, and 23.0% total nonstarch polysaccharides, respectively. The in vitro digestibility of DM for wDDGS1, wDDGS2, and cDDGS was 67.7, 72.1, and 59.6%, respectively. The cDDGS had greater ( < 0.05) total gas and VFA production than both wheat DDGS. The wDDGS2 had lower ( < 0.05) total gas production than wDDGS1. Multicarbohydrase increased ( < 0.05) total gas production for cDDGS and total VFA production for wDGGS1 but did not increase gas or VFA production for wDDGS2. Addition of protease with multicarbohydrase to DDGS reduced ( < 0.05) total gas and VFA productions and increased ( < 0.05) branched-chain VFA regardless of DDGS type. Confocal laser scanning microscopy and scanning electron microscopy revealed that DDGS were mainly aggregates of resistant and nonfermentable starchy and nonstarchy complexes formed during DDGS production. After in vitro fermentation with porcine fecal inoculum, particles of enzyme-treated DDGS were generally smaller than those of the untreated DDGS. In conclusion, cDDGS had a more porous matrix that was more fermentable than the wheat DDGS. The wDDGS2 was less fermentable than wDDGS1. Multicarbohydrase increased fermentability of cDDGS and wDDGS1 but not wDDGS2, indicating that its efficacy in DDGS is dependent on matrix porosity and DDGS source. Protease hindered efficacy of multicarbohydrase.

Myrosinase Compatible Simultaneous Determination of Glucosinolates and Allyl Isothiocyanate by Capillary Electrophoresis Micellar Electrokinetic Chromatography (CE-MEKC)

INTRODUCTION

The functional food Cruciferous vegetables contain glucosinolates which are decomposed by the myrosinase enzyme upon tissue damage. The isothiocyanates are the most frequent decomposition products. Because of their various bioactivities, these compounds and the myrosinase is of high interest to many scientific fields.

OBJECTIVE

Development of a capillary electrophoresis method capable of myrosinase-compatible, simultaneous quantification of glucosinolates and isothiocyanates.

METHODS

Capillary electrochromatography parameters were optimised, followed by optimisation of a myrosinase-compatible derivatisation procedure for isothiocyanates. Vegetable extracts (Brussels sprouts, horseradish, radish and watercress) were tested for myrosinase activity, glucosinolate content and isothiocyanate conversion rate. Allyl isothiocyanate was quantified in some food products.

RESULTS

The method allows quantification of sinigrin, gluonasturtiin and allyl isothiocyanate after myrosinase compatible derivatisation in-vial by mercaptoacetic acid. The chromatograhpic separation takes 2.5 min (short-end injection) or 15 min (long-end injection). For the tested vegetables, measured myrosinase activity was between 0.960-27.694 and 0.461-26.322 µmol/min/mg protein, glucosinolate content was between 0-2291.8 and 0-248.5 µg/g fresh weight for sinigrin and gluconastrutiin, respectively. The possible specificity of plants to different glucosinolates was also shown. Allyl isothiocyanate release rate was different in different vegetables (73.13 - 102.13%). The method could also be used for quantification of allyl isothiocyanate from food products.

CONCLUSIONS

The presented capillary electrophoresis method requires a minimal amount of sample and contains only a few sample preparation steps, and can be used in several applications (glucosinolate determination, myrosinase activity measurement, isothiocyanate release estimation). Copyright © 2016 John Wiley & Sons, Ltd.

A Chromogenic Assay Suitable for High-Throughput Determination of Limit Dextrinase Activity in Barley Malt Extracts

Twenty-four malt samples were assayed for limit dextrinase activity using a chromogenic assay developed recently in our group. The assay utilizes a small soluble chromogenic substrate which is hydrolyzed selectively by limit dextrinase in a coupled assay to release the chromophore 2-chloro-4-nitrophenol. The release of the chromophore, corresponding to the activity of limit dextrinase, can be followed by measuring the UV absorption at 405 nm. The 24 malt samples represented a wide variation of limit dextrinase activities, and these activities could be clearly differentiated by the assay. The results obtained were comparable with the results obtained from a commercially available assay, Limit-Dextrizyme from Megazyme International Ireland. Furthermore, the improved assay uses a soluble substrate. That makes it well suited for high-throughput screening as it can be handled in a 96-well plate format.

Seasonal Dynamics of Soil Labile Organic Carbon and Enzyme Activities in Relation to Vegetation Types in Hangzhou Bay Tidal Flat Wetland

Soil labile organic carbon and soil enzymes play important roles in the carbon cycle of coastal wetlands that have high organic carbon accumulation rates. Soils under three vegetations (Phragmites australis, Spartina alterniflora, and Scirpusm mariqueter) as well as bare mudflat in Hangzhou Bay wetland of China were collected seasonally. Seasonal dynamics and correlations of soil labile organic carbon fractions and soil enzyme activities were analyzed. The results showed that there were significant differences among vegetation types in the contents of soil organic carbon (SOC) and dissolved organic carbon (DOC), excepting for that of microbial biomass carbon (MBC). The P. australis soil was with the highest content of both SOC (7.86 g kg^-1) and DOC (306 mg kg^-1), while the S. mariqueter soil was with the lowest content of SOC (6.83 g kg^-1), and the bare mudflat was with the lowest content of DOC (270 mg kg^-1). Soil enzyme activities were significantly different among vegetation types except for urease. The P. australis had the highest annual average activity of alkaline phosphomonoesterase (21.4 mg kg^-1 h^-1), and the S. alterniflora had the highest annual average activities of β-glycosidase (4.10 mg kg^-1 h^-1) and invertase (9.81mg g^-1 24h^-1); however, the bare mudflat had the lowest activities of alkaline phosphomonoesterase (16.2 mg kg^-1 h^-1), β-glycosidase (2.87 mg kg^-1 h^-1), and invertase (8.02 mg g^-1 24h^-1). Analysis also showed that the soil labile organic carbon fractions and soil enzyme activities had distinct seasonal dynamics. In addition, the soil MBC content was significantly correlated with the activities of urease and β-glucosidase. The DOC content was significantly correlated with the activities of urease, alkaline phosphomonoesterase, and invertase. The results indicated that vegetation type is an important factor influencing the spatial-temporal variation of soil enzyme activities and labile organic carbon in coastal wetlands.

Determination of lytic enzyme activities of indigenous Trichoderma isolates from Pakistan

This study investigated lytic enzyme activities in three indigenous Trichoderma strains namely, Trichoderma asperellum, Trichoderma harzianum and Trichoderma sp. Native Trichoderma strains and a virulent strain of Rhizoctonia solani isolated from infected bean plants were also included in the study. Enzyme activities were determined by measuring sugar reduction by dinitrosalicylic acid (DNS) method using suitable substrates. The antagonists were cultured in minimal salt medium with the following modifications: medium A (1 g of glucose), medium B (0.5 g of glucose + 0.5 g of deactivated R. solani mycelia), medium C (1.0 g of deactivated respective antagonist mycelium) and medium D (1 g of deactivated R. solani mycelia). T asperellum showed presence of higher amounts of chitinases, β-1, 3-glucanases and xylanases in extracellular protein extracts from medium D as compared to medium A. While, the higher activities of glucosidases and endoglucanses were shown in medium D extracts by T. harzianum. β-glucosidase activities were lower compared with other enzymes; however, activities of the extracts of medium D were significantly different. T. asperellum exhibited maximum inhibition (97.7%). On the other hand, Trichoderma sp. did not show any effect on mycelia growth of R. solani on crude extract.

Influence of the insecticides acetamiprid and carbofuran on arylamidase and myrosinase activities in the tropical black and red clay soils

The objective of this study was to determine the effects of two insecticides, namely, acetamiprid and carbofuran on the enzymatic activities of arylamidase (as glucose formed from sinigrin) and myrosinase (as β-naphthylamine formed from L-leucine β-naphthylamide) in the black and red clay soils collected from a fallow groundnut (Arachis hypogaea L.) fields in the Anantapur District, Andhra Pradesh, India. The study was realized within the framework of the laboratory experiments in which the acetamiprid and carbofuran were applied to the soils at different doses (1.0, 2.5, 5.0, 7.5, 10.0 kg ha(-1)). Initially, the physicochechemical properties of the soil samples were analyzed. After 10 days of pesticide application, the soil samples were analyzed for the enzyme activities. Acetamiprid and carbofuran stimulated the arylamidase and myrosinase activities at lower concentrations after 10 days incubation. Striking stimulation in soil enzyme activities was noticed at 2.5 kg ha(-1), persists for 20 days in both the soils. Overall, higher concentrations (5.0-10.0 kg ha(-1)) of acetamiprid and carbofuran were toxic or innocuous to the arylamidase and myrosinase activities. Nevertheless, the outcomes of the present study clearly indicate that the use of these insecticides (at field application rates) in the groundnut fields (black and red clay soils) stimulated the enzyme (arylamidase and myrosinase) activities.

Spatio-temporal appearance of α-amylase and limit dextrinase in barley aleurone layer in response to gibberellic acid, abscisic acid and salicylic acid

BACKGROUND

Cereal seed germination involves mobilization of storage reserves in the starchy endosperm to support seedling growth. In response to gibberellin produced by the embryo the aleurone layer synthesizes hydrolases that are secreted to the endosperm for degradation of storage products. In this study analysis of intracellular protein accumulation and release from barley aleurone layers is presented for the important enzymes in starch degradation: α-amylase and limit dextrinase (LD).

RESULTS

Proteins were visualized by immunoblotting in aleurone layers and culture supernatants from dissected aleurone layers incubated up to 72 h with either gibberellic acid (GA), abscisic acid (ABA) or salicylic acid (SA). The results show that α-amylase is secreted from aleurone layer treated with GA soon after synthesis but the release of LD to culture supernatants was significantly delayed and coincided with a general loss of proteins from aleurone layers.

CONCLUSIONS

Release of LD was found to differ from that of amylase and was suggested to depend on programmed cell death (PCD). Despite detection of intracellular amylase in untreated aleurone layers or aleurone layers treated with ABA or SA, α-amylase was not released from these samples. Nevertheless, the release of α-amylase was observed from aleurone layers treated with GA+ABA or GA+SA.

Proteomic analysis of the excretory-secretory products from larval stages of Ascaris suum reveals high abundance of glycosyl hydrolases

BACKGROUND

Ascaris lumbricoides and Ascaris suum are socioeconomically important and widespread parasites of humans and pigs, respectively. The excretory-secretory (ES) molecules produced and presented at the parasite-host interface during the different phases of tissue invasion and migration are likely to play critical roles in the induction and development of protective immune and other host responses.

METHODOLOGY/PRINCIPAL FINDINGS

The aim of this study was to identify the ES proteins of the different larval stages (L3-egg, L3-lung and L4) by LC-MS/MS. In total, 106 different proteins were identified, 20 in L3-egg, 45 in L3-lung stage and 58 in L4. Although most of the proteins identified were stage-specific, 15 were identified in the ES products of at least two stages. Two proteins, i.e. a 14-3-3-like protein and a serpin-like protein, were present in the ES products from the three different larval stages investigated. Interestingly, a comparison of ES products from L4 with those of L3-egg and L3-lung showed an abundance of metabolic enzymes, particularly glycosyl hydrolases. Further study indicated that most of these glycolytic enzymes were transcriptionally upregulated from L4 onwards, with a peak in the adult stage, particularly in intestinal tissue. This was also confirmed by enzymatic assays, showing the highest glycosidase activity in protein extracts from adult worms gut.

CONCLUSIONS/SIGNIFICANCE

The present proteomic analysis provides important information on the host-parasite interaction and the biology of the migratory stages of A. suum. In particular, the high transcriptional upregulation of glycosyl hydrolases from the L4 stage onwards reveals that the degradation of complex carbohydrates forms an essential part of the energy metabolism of this parasite once it establishes in the small intestine.

Crystallization and preliminary X-ray diffraction analysis of a new xyloglucanase from Xanthomonas campestris pv. campestris

Xyloglucanases (Xghs) are important enzymes involved in xyloglucan modification and degradation. Xanthomonas campestris pv. campestris (Xcc) is a phytopathogenic bacterium which produces a large number of glycosyl hydrolases (GH), but has only one family 74 GH (Xcc-Xgh). This enzyme was overexpressed in Escherichia coli, purified and crystallized. Diffraction data sets were collected for the native enzyme and its complex with glucose to maximum resolutions of 2.0 and 2.1 Å, respectively. The data were indexed in a hexagonal crystal system with unit-cell parameters a = b = 153.4, c = 84.9 Å. As indicated by molecular-replacement solution, the crystals belonged to space group P6(1).

Revised determination of free and complexed myrosinase activities in plant extracts

The enzyme myrosinase (thioglucoside glucohydrolase, EC 3.2.1.147, formerly EC 3.2.3.1) catalyzes the hydrolysis of glucosinolates after tissue damage in plants of the order Brassicales. The various myrosinase isoforms occur either as free soluble dimers or as insoluble complexes. We propose a reliable method for determination of both soluble and insoluble myrosinase activity concentrations in partially purified plant extracts. The procedure requires the removal of endogenous glucosinolates through ion-exchange columns previous to enzyme measurements. Myrosinase activity was assayed in continuous mode by photometric quantification of the released glucose using glucose-oxidase with peroxidase and colorimetric indicators. The measurement of the colored product at 492nm has a favorable signal to noise ratio both in clear extract solutions (free dimers) and in turbid pellet suspensions (insoluble complexes). No interferences by ascorbic acid were found in continuous analyses. With the recommended sample preparation methods and assay conditions potential activities in damaged plant tissues can be characterized which are involved in plant defense mechanisms.

[Investigation of fucoidanase by FTIR spectra]

Fucoidanase was isolated and purified from marine fungus LD8 by solid state fermentation, extraction with citric acid buffer, acetone precipitatation and column chromatography on Sephadex G-100. A single band on PAGE shows that pretty pure fucoidanase has been obtained. FT-IR spectra and its derivation, self-deconvolution and curve-fitting methods were used to analyze the secondary structure of the fucoidanase. Composite bands of the amide I and amide III were studied by using Fourier self-deconvolution (FSD) with an enhancement factor of K = 2.2 and a half width of 20.2 cm(-1). The relative average fractions of alpha-helix, beta-sheet, random coil, beta-turn are 11.5%, 58.6%, 14.5% and 15.9%, respectively, according to amide I region, while the content of alpha-helix is 12%, beta-sheet 57.3%, random coil 14.5%, and beta-turn 16.3% on amide III region. In other words, both the conclusions were exactly consistent. All the above results show that beta-sheet was the dominant component, which is about 58%, and that beta-turn is about 15%, random coil 15%, and alpha-helix 12% at room temperature.

Synthesis of substituted septanosyl-1,2,3-triazoles

A carbohydrate-based oxepine, derived from 2-deoxy-D-arabino-hexopyranose, was used to prepare a family of septanosyl-1,2,3-triazoles in four steps. DMDO mediated epoxidation of the oxepine followed by trapping of the intermediate 1,2-anhydroseptanose by sodium azide gave the beta-substituted glycosyl azide. The septanosyl azide was then reacted with a number of alkynes under thermal Huisgen or copper(I) mediated reaction conditions. Hydrogenolysis of benzyl protecting groups gave substituted septanosyl-1,2,3-triazoles. The new septanose-based structures were then evaluated as potential glycosidase inhibitors.

Two small enzyme isoforms mediate mammalian mitochondrial poly(ADP-ribose) glycohydrolase (PARG) activity

Poly(ADP-ribose)glycohydrolase (PARG) is the major enzyme capable of rapidly hydrolyzing poly(ADP-ribose) (PAR) formed by the diverse members of the PARP enzyme family. This study presents an alternative splice mechanism by which two novel PARG protein isoforms of 60 kDa and 55 kDa are expressed from the human PARG gene, termed hPARG60 and hPARG55, respectively. Homologous forms were found in the mouse (mPARG63 and mPARG58) supporting the hypothesis that expression of small PARG isoforms is conserved among mammals. A PARG protein of approximately 60 kDa has been described for decades but with its genetic basis unknown, it was hypothesized to be a product of posttranslational cleavage of larger PARG isoforms. While this is not excluded entirely, isolation and expression of cDNA clones from different sources of RNA indicate that alternative splicing leads to expression of a catalytically active hPARG60 in multiple cell compartments. A second enzyme, hPARG55, that can be expressed through alternative translation initiation from hPARG60 transcripts is strictly targeted to the mitochondria. Functional studies of a mitochondrial targeting signal (MTS) in PARG exon IV suggest that hPARG60 may be capable of shuttling between nucleus and mitochondria, which would be in line with a proposed function of PAR in genotoxic stress-dependent, nuclear-mitochondrial crosstalk.

Improvement of a β-glucanase activity test by taking into account the batch reactor balance of the test system

Activity tests of enzymes are often applied for determining their concentration. In the easiest case, just one product concentration is measured after a given time. This often leads to nonlinear dependences of the apparent activity with enzyme protein concentration. A general solution of this problem consists in using the balance equation of the assay system, which commonly represents a batch reactor. Here, the balance equation of the batch for a general Michaelis Menten-type reaction kinetics is used as the calibration function. The correlation of the apparent activity and enzyme concentration was established by capturing the enzyme by means of metal chelate interaction owing to a hexahistidine tag attached to the beta-glucanase.

Novel insoluble dye-labeled substrates for screening inulin-degrading microorganisms

Inulin hydrogels were used to prepare insoluble colored substrates for screening of inulin-degrading microorganisms. Methycrylated inulin, synthesized with glycidyl methacrylate, was crossed-linked by free radical polymerization producing an insoluble hydrogel. The inulin hydrogels were colored with one of three covalent dyes (Reactive blue 4, Reactive orange 14, Reactive red 120). The efficacy of the colored inulin hydrogels was determined by comparing their performance to insoluble, colored amylose, xylan and HE-cellulose in screening assays. Novel substrates (alone or in combination with other insoluble colored substrates) were successfully used for screening inulin-degrading microorganisms from sludge samples. Selected strains were identified using 16S rDNA gene partial sequencing; all of them belong to the genus Bacillus.

[Effects of DMPP-compound fertilizer on greenhouse celery growth and nutritional quality]

A field study with greenhouse celery (Apium graveolens L. ) showed that compared with basal application of ordinary compound fertilizer, one-time basal application of DMPP-compound fertilizer ( ENTEC , 12-12-17) at the rates of 67. 5 kg N x hm(-2) and 54. 0 kg N x hm(-2) increased the yield by 5. 78% and 10. 14% , respectively. The application of ENTEC also improved the nutritional quality of edible parts, e. g. , the Vc, amino acid, soluble sugar, N and P contents increased, while nitrate content decreased. Compared with basal plus side dressing applications, appropriately reducing the application rate and times of ENTEChad more beneficial effects on celery yield and quality, and reduced the production costs. ENTEC could suppress the transformation of soil NH4+ -N to NO3 - -N effectively, and thus, its application could retain soil residual N more in NH4+ -N than in NO3- -N form after celery harvested, resulting in a reduction of nitrate leaching.

Midgut protease activities in monophagous larvae of Apollo butterfly, Parnassius apollo ssp. frankenbergeri

We assayed the relative activities of midgut proteolytic enzymes in individuals of the fourth (L(4)) and fifth (L(5)) instar of Apollo larvae, inhabiting Pieniny Mts (southern Poland). The comparisons between midgut tissue with glicocalyx (MT) and liquid midgut contents with peritrophic membrane (MC) were made. Optimal media pHs of the assayed proteolytic enzymes in P. apollo midgut samples were similar to those of other lepidopteran species. Endopeptidases, as well as carboxypeptidases, digested effectively in alkaline environment, while aminopeptidases were active in a broad pH range. Trypsin is probably the main endoprotease (correlation with caseinolytic activity in MC of L(5) larvae: r=0.606; p=0.004); however, its activity was low as compared with that in other leaf-eating Lepidoptera. This suggests a minor role of trypsin and chymotrypsin in protein digestion in Apollo larvae, probably due to limited availability of the leaf proteins. Instead, due to very high carboxypeptidase A activity in midgut tissue, the larvae obtain exogenous amino acids either directly or from oligopeptides and glycoproteins. High and significant positive correlations between the enzyme activity and glucosidase as well as galactosidase activities strongly support this opinion.

Purification and Characterization of Two Types of Chitosanase from a Microbacterium sp

Two extracellular chitosanases (ChiX and ChiN) were extracted from Microbacterium sp. OU01 with Mr values of 81 kDa (ChiX) and 30 kDa (ChiN). ChiN was optimally active at pH 6.2 and 50 degrees C and ChiX at pH 6.6 and 60 degrees C (assayed over 15 min). Both the activities increased with the degree of deacetylation (DDA) of chitosan. ChiN hydrolyzed oligomers of glucosamine (GlcN) larger than chitopentaose, and chitosan with 62-100% DDA; but ChiX acted on chitosan and released GlcN. Hydrolysis of chitosan with 99% DDA by ChiN released chitobiose, chitotriose and chitotetraose as the major products.

Enhancing thermostability of maltogenic amylase from Bacillus thermoalkalophilus ET2 by DNA shuffling

DNA shuffling was used to improve the thermostability of maltogenic amylase from Bacillus thermoalkalophilus ET2. Two highly thermostable mutants, III-1 and III-2, were generated after three rounds of shuffling and recombination of mutations. Their optimal reaction temperatures were all 80 degrees C, which was 10 degrees C higher than that of the wild-type. The mutant enzyme III-1 carried seven mutations: N147D, F195L, N263S, D311G, A344V, F397S, and N508D. The half-life of III-1 was about 20 times greater than that of the wild-type at 78 degrees C. The mutant enzyme III-2 carried M375T in addition to the mutations in III-1, which was responsible for the decrease in specific activity. The half-life of III-2 was 568 min while that of the wild-type was < 1 min at 80 degrees C. The melting temperatures of III-1 and III-2, as determined by differential scanning calorimetry, increased by 6.1 degrees C and 11.4 degrees C, respectively. Hydrogen bonding, hydrophobic interaction, electrostatic interaction, proper packing, and deamidation were predicted as the mechanisms for the enhancement of thermostability in the enzymes with the mutations.

Purification and properties of a heat-stable exoinulinase isoform from Aspergillus fumigatus

An inducible extracellular exoinulinase (isoform II) was purified from the extracellular extract of Aspergillus fumigatus by ammonium sulphate precipitation, followed by successive chromatographies on DEAE-Sephacel, Octyl-Sepharose (HIC), Sephacryl S-200, affinity chromatography on ConA-CL Agarose and Sephacryl S-100 columns. The enzyme was purified 75-folds with 3.2% activity yield from the starting culture broth. The purified isoform II was a monomeric 62 kDa protein with a pI value of 4.5. The enzyme showed maximum activity at pH 6.0 and was stable over a pH range of 4.0-7.0, whereas the optimum temperature for enzyme activity was 60 degrees C. The inulinase isoform II showed exo-inulinolytic activity and retained 72% and 44% residual activity after 12 h at 60 degrees C and 70 degrees C, respectively. The inulin hydrolysis activity was completely abolished with 5 mM Hg2+ and Fe2+, whereas K+ and Cu2+ enhanced the inulinase activity. As compared to sucrose, stachyose and raffinose the purified enzyme had a lower Km (1.25 mM) and higher catalytic center activity (Kcat = 3.47 x 10(4) min(-1)) for inulin. As compared to exoinulinase isoform I of A. fumigatus, purified earlier, the isoform II is more thermostable and is a potential candidate for commercial production of fructose from inulin.

Mapping of an internal protease cleavage site in the Ssy5p component of the amino acid sensor of Saccharomyces cerevisiae and functional characterization of the resulting pro- and protease domains by gain-of-function genetics

Ssy5p is a 77-kDa protein believed to be a component of the SPS amino acid sensor complex in the plasma membrane of Saccharomyces cerevisiae. Ssy5p has been suggested to be a chymotrypsin-like serine protease that activates the transcription factor Stp1p upon exposure of the yeast to extracellular amino acid. Here we overexpressed and partially purified Ssy5p to improve our understanding of its structure and function. Antibodies against Ssy5p expressed in Escherichia coli were isolated and used to detect Ssy5p processing in S. cerevisiae cells. Partial purification and N-terminal sequencing of processed Ssy5p revealed in vivo cleavage of Ssy5p between amino acids 381 and 382. We also isolated constitutively signaling SSY5 mutants and quantified target promoter activation and Stp1p processing. One mutant contained an amino acid substitution in the prodomain, whereas three others harbored amino acid substitutions in the protease domain. Dose-response analysis indicated that all four mutants exhibited increased basal levels of Stp1p processing. Interestingly, whereas the three constitutive mutants mapping to the protease domain of Ssy5p exhibited the decreased 50% effective concentration (EC(50)) characteristic of constitutive mutations previously found in Ssy1p, Ptr3p, and Ssy5p, the EC(50) of the mutation that maps to the prodomain of Ssy5p remained essentially unchanged. In a model of Ssy5p derived from its similarities with alpha-lytic protease from Lysobacter enzymogenes, the sites corresponding to the mutations in the protease domain are clustered in a region facing the prodomain, suggesting that this region interacts with the prodomain and participates in the conformational dynamics of sensing.

Deglycosylation of human glycoconjugates by the sequential activities of exoglycosidases expressed by Streptococcus pneumoniae

Streptococcus pneumoniae produces three surface-associated exoglycosidases; a neuraminidase, NanA, a beta-galactosidase, BgaA, and a beta-N-acetylglucosaminidase, StrH. the proposed functions of NanA, which removes terminal sialic acid, include revealing receptors for adherence, affecting the function of glycosylated host clearance molecules, modifying the surface of other bacteria coinhabiting the same niche, and providing a nutrient source. However, it is unclear whether following desialylation S. pneumoniae can further deglycosylate human targets through the activity of BgaA or StrH. We demonstrate that NanA, BgaA and StrH act sequentially to remove sialic acid, galactose and N-acetylglucosamine and expose mannose on human glycoproteins that bind to the pneumococcus and protect the airway. In addition, both BgaA and NanA were shown to contribute to the adherence of unencapsulated pneumococci, to human epithelial cells. Despite these findings, triple exoglycosidase mutants colonized mice as well as their parental strains, suggesting that any effect of these genes on colonization and disease may be host species-specific. These studies highlight the importance of considering the complete ability of S. pneumoniae to deglycosylate human targets and suggest that in addition to NanA, BgaA and StrH also contribute to pneumococcal colonization and/or pathogenesis.

Estimation of bound and free fractions of lignocellulose-degrading enzymes of wood-rotting fungi Pleurotus ostreatus, Trametes versicolor and Piptoporus betulinus

Liquid cultures with cellulose and solid state fermentation cultures on wheat straw of the white-rot fungi Pleurotus ostreatus and Trametes versicolor and the brown-rot fungus Piptoporus betulinus were assayed for the free and solid fraction-bound activity of lignocellulose-degrading enzymes. The majority of the ligninolytic enzymes laccase and Mn peroxidase was detected in the free fraction of P. ostreatus and T. versicolor. The endocleaving enzymes endo-1,4-beta-glucanase, endo-1,4-beta-mannanase and endo-1,4-beta-xylanase were detected almost exclusively in the free fraction, while significant amounts of 1,4-beta-glucosidase, cellobiohydrolase, 1,4-beta-xylosidase and 1,4-beta-mannosidase were present in the bound fraction depending on the mode of cultivation and the species. The bound enzymes accounted for 66% of the total activity in P. ostreatus straw cultures, 35% in T. versicolor and only 8% in P. betulinus. The enzymes also showed significant differences in freeze-drying stability. Hydrolases in general showed high stability, whereas laccase and Mn peroxidase of P. ostreatus were the least stable.

Assessment of salivary levels of the chosen exoglycosidases in patients with aggressive periodontitis after treatment with doxycycline

PURPOSE

The aim of the study was the clinical assessment of the periodontium in patients with aggressive periodontitis (AP) after treatment with doxycycline hyclate. Moreover, an attempt was made to evaluate the effect of the treatment on the salivary concentrations of beta-glucuronidase, HEX, HEX A and HEX B in AP patients.

MATERIAL AND METHODS

Sixteen patients with aggressive periodontitis, aged 28-45 years, were enrolled in the study. The patients were treated with a doxycycline hyclate preparation (Periostat) for 2 months at a dose of 20 mg twice a day. The clinical examination was performed twice, directly prior to pharmacological treatment and after its termination. The following clinical parameters were evaluated: the plaque index (PI), the sulcus bleeding index (SBI), the pocket probing depth (PPD) and the clinical attachment level (CAL). Biochemical determination of beta-glucuronidase, HEX, HEX A and HEX B concentrations in non-stimulated saliva was performed before and after treatment.

RESULTS

In AP patients, the values of PI, SBI and CAL before and after treatment were comparable. The mean pocket probing depth before treatment was 3.5 mm, which decreased significantly after treatment (3.2 mm). The values expressed as pKat/kg protein for specific enzymatic activities of HEX, HEX A, HEX B and beta-glucuronidase in the saliva of AP patients before and after doxycycline treatment were similar.

CONCLUSIONS

A 2-month treatment with doxycycline is too short to obtain clinical changes. Although the assessment of the activity of such enzymes as beta-glucuronidase, HEX, HEX A and HEX B in the saliva of AP patients allows detection of periodontal inflammation, it cannot be used to determine the risk of its development and therefore has no practical significance.

Acid glycosidases in the isthmus of the hen oviduct and egg shell membranes

Specific activities of seven acid glycosidases: beta-hexosaminidase, alpha- and beta-galactosidase, alpha- and beta-mannosidase, alpha-glucosidase and alpha-fucosidase were determined in various parts of the domestic hen oviduct (infundibulum, isthmus, shell gland and vagina). The activity of most enzymes was the highest in the isthmus. Multiple forms of all acid glycosidases from the isthmus were separated by strong anion exchange chromatography at pH 6.0. The isoelectric points of the isthmus forms of beta-hexosaminidase, beta-galactosidase and alpha- and beta-mannosidase were determined by chromatofocusing. For the first time the high beta-galactosidase activity was found in hen egg shell membranes.

Activity of lysosomal exoglycosidases in saliva of patients with HIV infection

INTRODUCTION

The aim of this work was to evaluate the influence of HIV infection on the catabolism of glycoconjugates in oral cavity, by determination the activity of lysosomal exoglycosidases in resting whole saliva HIV positive patients.

MATERIAL AND METHODS

Sample of resting whole saliva from HIV infected patients (divided into two groups, depending on lymphocyte CD4+ number in peripheral blood) and the control-HIV negative group were analyzed for exoglycosidases activity. Determinations the activities (muKat/kg of protein) of lysosomal exoglycosidases were performed according to Chatteriee et al., modified Zwierz et al. The protein content (mg/ml) was determined by the Lowry method. Statistical analysis was performed using packet Statistica 6.0. Results were expressed as the mean and SD. P values less than 0.05 were considered significant.

RESULTS

Exoglycosidases activities were not statistically dependent on immunological status of HIV patients. We obtained insignificant increase activities of HEX, HEX A and GALp and insignificant decrease activity of HEX B along with the reduction of the CD4+ number. In both HIV positive groups the activities of HEX B were statistically lower and GALp statistically higher in comparison to the control. In the case of HEX A significant differences could be observed between patients with low immunological status and the control group.

CONCLUSIONS

HIV infection intensifies catabolism glycoconiugates in saliva and changes activities of HEX, its isoenzymes A and B and beta-galactosidase. It may change susceptibility the cells lining oral cavity to viral and bacterial infections.

Enzymatic analysis of Blomia tropicalis and Blomia kulagini (Acari: Echimyopodidae) allergenic extracts obtained from different phases of culture growth

The majority of important allergenic extracts from arthropods present enzymatic activity. This activity has been studied particularly in Dermatophagoides house dust mites because of its implication in the stability and immunogenicity of extracts used as tools for the diagnosis and specific treatment of allergic diseases. Extracts from cultures of Blomia tropicalis [van Bronswijk (1973a, b). Acarologia 15:477-489, 490-505] and Blomia kulagini (Zakhvatkin 1936) were used to study enzymatic profiles during three growth periods of the mite population: latency phase, maximum mite concentration during exponential growth, and drop stage. The activities of 19 enzymes were analyzed using the Api Zym system. The results show a large variety of enzymes. Some enzymatic activity was found to be (almost) exclusively attributable to mites. The activity levels of proteases, glycosidases and lipases overlapped with the growth curve. Only phosphatase activity showed no significant change during mite growth when compared with the culture medium. We suggest that the glycosidases (beta-galactosidase, beta-glucuronidase, beta-N-acetylglucosaminidase, alpha-mannosidase and alpha-fucosidase) and proteases (leucine aminopeptidase and trypsin) may constitute suitable parameters for inclusion in the quality control process for the production of allergenic mite extracts, and may help define a new index for conducting environmental controls.

Distribution of acid glycosidases in the male genital tract of the pheasant

The distribution of the activity of seven acid glycosidases in the reproductive organs of the pheasant (Phasianus colchicus) was studied. The study was carried out on seven mature birds at the age of 11 months during the reproductive season (May). Significant (p<0.01) differences in acid glycosidase activity dependent on enzyme origin were observed. Generally, the highest activity of acid glycosidases was found in the epididymis, intermediate in the ductus deferens and the lowest in the testes. Exceptionally, alpha-mannosidase had the highest activity in the ductus deferens. Anion-exchange chromatography elution profiles of most enzymes from the tested reproductive organs were similar, however evident differences were observed for beta-mannosidase forms.

Cloning and sequencing of an exoglucanase gene from Streptomyces sp. M 23, and its expression in Streptomyces lividans TK-24

A gene encoding exoglucanase (CBHII) of Streptomyces sp. M 23 was cloned and sequenced. The cbhII gene consisted of 1359 bp capable of encoding a polypeptide of 453 amino acids with a calculated molecular mass of 45,175 Da. The deduced amino acid sequence showed homology with those of cellulases belonging to family 6 of the glycosyl hydrolases. The cbhII gene was subcloned into the plasmid pSEV1 and expressed in Streptomyces lividans TK-24. The transformed cells were able to secrete the enzyme efficiently in an active form. The CBHII expressed by S. lividans TK-24 was purified to homogeneity by SDS-polyacrylamide gel and characterized. The recombinant CBHII was stable up to 50 degrees C and more than 30% of the original activity remained after heating at 100 degrees C for 10 min. The amino-terminal amino acid sequence of the recombinant CBHII was identified as GPAAPTARVD. These results agreed well with the properties of the authentic CBHII.

Association of the GTP-binding protein Gtr1p with Rpc19p, a shared subunit of RNA polymerase I and III in yeast Saccharomyces cerevisiae

Yeast Gtr1p and its human homolog RRAG A belong to the Ras-like small G-protein superfamily and genetically interact with RCC1, a guanine nucleotide exchange factor for Ran GTPase. Little is known regarding the function of Gtr1p. We performed yeast two-hybrid screening using Gtr1p as the bait to find interacting proteins. Rpc19p, a shared subunit of RNA polymerases I and III, associated with Gtr1p. The association of Gtr1p with Rpc19p occurred in a GTP-form-specific manner. RRAG A associated with RPA16 (human Rpc19p homolog) in a GTP-form-specific manner, suggesting that the association is conserved during evolution. Ribosomal RNA and tRNA synthesis were reduced in the gtr1Delta strain expressing the GDP form of Gtr1p, but not the GTP form of Gtr1p. Gel-filtration studies revealed an accumulation of the smaller Rpc19p-containing complex, but not of A135, in the gtr1Delta strain. Here, we propose that Gtr1p is involved in RNA polymerase I and III assembly by its association with Rpc19p and could be a mediator that links growth regulatory signals with ribosome biogenesis.

Production and characterization of hemicellulase activities from Trichoderma harzianum strain T4

Xylan and mannan are the major constituent groups of hemicellulose in the cell wall of higher plants. The mesophilic fungus Trichoderma harzianum strain T4 produces extracellular xylanase and mannanase activities when grown in the presence of oat (Avena sativa)-spelt xylan and wheat bran as the carbon sources respectively. After the growth procedure, the crude extracts were submitted to ultrafiltration in an Amicon system fitted with a 10 kDa-cut-off membrane. Mannanase activity was only detected in the concentrated sample, whereas xylanase was also found in the permeate after ultrafiltration. Xylanase from the concentrated sample showed highest activity at 40 degrees C and pH 5.0. Mannanase activity was optimal at 65 degrees C and pH 2.6. Xylanase was stable in the temperature range 40-70 degrees C, presenting full stability for at least 48 h. Xylanase retained 100% of its original activity after incubation for 48 h at 70 degrees C. Xylanase was also stable at pH 5.0 and 6.0 for 48 h. However, mannanase activity was markedly less stable. The enzyme lost 50% of its activity at 55 degrees C after 45 min, whereas at 60 degrees C its half-life was 20 min. The Michaelis-Menten constant K(m) and V(max) for mannanase and xylanase activities were also calculated. Xylanase had more affinity for soluble xylan, with K(m) and V(max) values of 1.61 mg/ml and 10.03 units/ml respectively. The K(m) and V(max) values for crude mannanase were 6.0 mg/ml and 20.1 units/ml respectively. Xylanase and mannanase were activated by dithiothreitol, L-cysteine and L-tryptophan. Xylanase was partially purified by gel-filtration (Sephadex G-50) and hydrophobic-interaction (Phenyl-Sepharose) chromatographies. The partially purified enzyme was stable over the pH range 5-7 and temperature range of 40-60 degrees C. It was more active on soluble oat-spelt xylan and was activated by dithiothreitol, L-cysteine and L-tryptophan.

Detection of infant faecal bifidobacteria by enzymatic methods

An enzyme-based assay was developed for the detection of bifidobacteria in infant faeces. Ninety-five samples from 51 breast-fed infants in the age between 3 and 276 days were investigated. Bifidobacteria and other bacterial groups were determined by cultivation and fluorescence in situ hybridisation (FISH). Faecal samples were examined for the activity of fructoso-6-phosphate phosphoketolase (F6PPK) and for other enzymatic reactions using the API-ZYM kit. Twenty-nine infants had high numbers of bifidobacteria (usually higher than 9 log CFU/g) in their faeces. Seventeen infants (35%) did not contain detectable amounts of bifidobacteria in their faecal samples. The remaining five individuals had low counts of bifidobacteria (3-6 log CFU/g). Most negative infants possessed major amounts of clostridia in their faecal flora. There were no significant differences among bifidobacterial counts obtained by cultivation and FISH, detection of F6PPK, alpha-galactosidase and alpha-glucosidase activities could routinely be used for the rapid and simple detection of bifidobacteria in infant faecal samples. Bifidobacterial colonies were identified using enzymatic tests and PCR procedure based on 16S rRNA gene sequences species-specific primers. In 14 samples, the identifications of individual isolates were compared with direct analyses of faeces using the nested PCR-denaturing gradient gel electrophoresis (nested DGGE) procedure. The results obtained in several cases are not identical. Bifidobacterium longum and Bifidobacterium breve were most frequently identified. Bifidobacteria-positive samples had high activities of alpha-galactosidase and alpha-glucosidase. On the contrary, negative samples missed either one or both of these enzymatic activities. While all positive samples tested showed distinctive fructose-6-phosphate phosphoketolase activity (F6PPK), none of the negative samples expressed F6PPK activity.