Characterization of a bifunctional alginate lyase as a new member of the polysaccharide lyase family 17 from a marine strain BP-2

OBJECTIVES

Bifunctional alginate lyase can efficiently saccharify alginate biomass and prepare functional oligosaccharides of alginate.

RESULTS

A new BP-2 strain that produces alginate lyase was screened and identified from rotted Sargassum. A new alginate lyase, Alg17B, belonging to the polysaccharide lyase family 17, was isolated and purified from BP-2 fermentation broth by freeze-drying, dialysis, and ion exchange chromatography. The enzymatic properties of the purified lyase were investigated. The molecular weight of Alg17B was approximately 77 kDa, its optimum reaction temperature was 40-45 °C, and its optimum reaction pH was 7.5-8.0. The enzyme was relatively stable at pH 7.0-8.0, with a temperature range of 25-35 °C, and the specific activity of the purified enzyme reached 4036 U/mg. A low Na+ concentration stimulated Alg17B enzyme activity, but Ca2+, Zn2+, and other metal ions inhibited it. Substrate specificity analysis, thin-layer chromatography, and mass spectrometry showed that Alg17B is an alginate lyase that catalyses the hydrolysis of sodium alginate, polymannuronic acid (polyM) and polyguluronic acid to produce monosaccharides and low molecular weight oligosaccharides. Alg17B is also bifunctional, exhibiting both endolytic and exolytic activities toward alginate, and has a wide substrate utilization range with a preference for polyM.

CONCLUSIONS

Alg17B can be used to saccharify the main carbohydrate, alginate, in the ethanolic production of brown algae fuel as well as in preparing and researching oligosaccharides.

Immobilization and characterization of carbonic anhydrase purified from E. coli MO1 and its influence on CO₂ sequestration

The present investigation entails the immobilisation and characterisation of Escherichia coli MO1-derived carbonic anhydrase (CA) and its influence on the transformation of CO₂ to CaCO₃. CA was purified from MO1 using a combination of Sephadex G-75 and DEAE cellulose column chromatography, resulting in 4.64-fold purification. The purified CA was immobilised in chitosan-alginate polyelectrolyte complex (C-A PEC) with an immobilisation potential of 94.5 %. Both the immobilised and free forms of the enzyme were most active and stable at pH 8.2 and at 37 °C. The K(m) and V(max) of the immobilised enzyme were found to be 19.12 mM and 416.66 μmol min⁻¹ mg⁻¹, respectively; whereas, the K(m) and V(max) of free enzyme were 18.26 mM and 434.78 μmol min⁻¹ mg⁻¹, respectively. The presence of metal ions such as Cu²⁺, Fe²⁺, and Mg²⁺ stimulated the enzyme activity. Immobilised CA showed higher storage stability and maintained its catalytic efficiency after repeated operational cycles. Furthermore, both forms of the enzyme were tested for targeted application of the carbonation reaction to convert CO₂ to CaCO₃. The amounts of CaCO₃ precipitated over free and immobilised CA were 267 and 253 mg/mg of enzyme, respectively. The results of this study show that immobilised CA in chitosan-alginate beads can be useful for CO₂ sequestration by the biomimetic route.

Identification of Petriella setifera LH and characterization of its crude carboxymethyl cellulase for application in denim biostoning

The phylogenetic tree of the partial elongation factor-1 alpha gene fits better than the partial 18S rDNA for generic classification. From the results of the molecular tree and analysis of morphological characters, Petriella setifera LH was identified. It can be induced to produce carboxymethyl cellulase (CMCase). The crude CMCase only shows a 44.1-kDa band by activity staining after SDS-PAGE. It is optimally active at 55°C and pH 6.0, and is stable from pH 5.0-8.0 and at 45°C or below. The crude CMCase, which is not affected by Co(2+), is strongly activated in the presence of 10 mM Na(+), K(+), Ca(2+), Mg(2+), EDTA, and Mn(2+). It is strongly inhibited by 10 mM Fe(2+), Pb(2+), Al(3+), Zn(2+), Ag(+), Fe(3+), and Cu(2+). When compared with denim treatment by Novoprime A800 (a commercial neutral cellulase), crude CMCase exhibits a similar fabric weight loss and indigo dye removal. These results indicate that crude CMCase has potential application in denim biostoning.

[Research progress of effect of anti-diabetic traditional Chinese medicines based on regulation of glucose metabolic enzyme]

Diabetes is a global threat threatening human health in the world, with an increasing incidence rate in recent years. The disorder of glucose metabolism is one of the major factors. As relevant glucose metabolic enzymes such as alpha-glucosidase, glucose-6-phosphatase (G-6-P), glycogen phosphorylase (GP) and glycogen synthase kinase-3 (GSK-3) get involved in and control the process of glucose metabolism, the regulation of the activity of glucose metabolic enzymes is of significance to the treatment of diabetes. Traditional Chinese medicines (TCMs) have been widely researched because of their low toxicology and high efficiency, and many extracts and components from TCMs have been proven to be regulators of glucose metabolic enzymes. Compared with anti-diabetic western medicines, anti-diabetic TCMs feature safety, reliability and low price. This essay summarizes the anti-diabetic effect of TCMs on regulating glucose metabolic enzymes.

Establishment of hypoglycemic agent screening method based on human glucokinase

OBJECTIVE

To establish a reliable platform for screening glucokinase activators (GKAs) in vitro.

METHODS

Pancreatic glucokinase (PGK) protein expressed in a prokaryotic expression system as a histidine-tagged fusion protein from Homo sapiens was produced. Then, response surface methodology (RSM) was used to optimize the microplate-based GKA screening platform. In the first step of optimization with Plackett-Burman design (PBD), initial pH, reaction time and MgCl2 were found to be important factors affecting the activity ratio of GKA (RO-28-1675) significantly. In the second step, a 2(3) full factorial central composite design (CCD) and RSM were applied to the optimal condition determination of each significant variable. A second-order polynomial was determined by a multiple regression analysis of the experimental data.

RESULTS

The following optimal values for the critical factors were obtained: initial pH 0 (7.0), reaction time-0.63 (13.7 min) and MgCl2 0.11 (2.11 mmol/L) with a predicted value of the maximum activity ratio of 34.1%.

CONCLUSION

Under the optimal conditions, the practical activity ratio is 34.8%. The determination coefficient (R2) is 0.9442, ensuring adequate credibility of the model. LLAE3, extracted from Folium nelumbinis in our laboratory, has prominently activated effects on PGK.

Effects of resin or charcoal treatment on fetal bovine serum and bovine calf serum

INTRODUCTION

Charcoal- or resin-stripping of fetal bovine serum (FBS) or bovine calf serum (BCS) intended for supplementation of cell culture media is widely practiced to remove a variety of endogenous compounds, including steroid, peptide, and thyroid hormones. The possibility that stripping removes other biologically relevant factors from serum may not be appreciated.

METHODS

In this report, standardized clinical laboratory testing methods were used to assess the effects of resin- and charcoal-stripping on content in FBS and BCS of more than 25 analytes in the sera.

RESULTS AND CONCLUSION

In addition to hormones, the serum constituents affected by stripping are certain vitamins, electrolytes, enzyme activities, and metabolites.

A CE assay for the detection of agonist-stimulated adenylyl cyclase activity

A CE assay was developed for the detection of adenylyl cyclase (AC) activity stimulated at the AC and G protein-coupled receptor (GPCR) level. In the assay, cell membranes overexpressing GPCR and/or AC were incubated with modulators and substrate ATP to produce cAMP in a dose-dependent manner. In both the CE-UV and a radiochemical assay, the addition of forskolin (FSK) resulted in a two- to three-fold maximum increase in AC activity with EC50s of 4.2 +/- 0.7 and 2.4 +/- 0.7 microM, respectively, demonstrating that similar results were obtained by both assays. GPCR activation was also detected using cell membranes overexpressing AC and the beta2-adrenergic receptor (beta2AR) fused to the stimulatory G protein. Terbutaline (beta2AR agonist) increased the basal rate of cAMP formation 1.7 +/- 0.1-fold resulting in an EC50 of 62 +/- 10 nM. The assay's ability to detect antagonists is demonstrated by the expected right-shifted EC50 of terbutaline by the beta2AR antagonist propranolol. The CE-UV assay offers advantages over the traditional radioactivity assay in terms of safety and labor.

Functional analysis of a lipid galactosyltransferase synthesizing the major envelope lipid in the Lyme disease spirochete Borrelia burgdorferi

One of the major lipids in the membranes of Borrelia burgdorferi is monogalactosyl diacylglycerol (MGalDAG), a glycolipid recently shown to carry antigenic potency. Herein, it is shown that the gene mgs (TIGR designation bb0454) of B. burgdorferi encodes for the protein bbMGS that, when expressed in Escherichia coli, catalyzes the glycosylation of 1,2-diacylglycerol with specificity for the donor substrate UDP-Gal yielding MGalDAG. Related lipid enzymes were found in many Gram-positive bacteria. The presence of this galactosyltransferase activity and synthesis of a cholesteryl galactoside by another enzyme were verified in B. burgdorferi cell extract. Besides MGalDAG, phosphatidylcholine, phosphatidylglycerol, and cholesterol were also found as major lipids in the cell envelope. The high isoelectric point of bbMGS and clustered basic residues in its amino acid sequence suggest that the enzyme interacts with acidic lipids in the plasma membrane, in agreement with strong enzymatic activation of bbMGS by phosphatidylglycerol. The membrane packing and immunological properties of MGalDAG are likely to be of great importance in vivo.

Purification and characterization of xylanases from Aspergillus giganteus

A strain of Aspergillus giganteus cultivated in a medium with xylan produced two xylanases (xylanase I and II) which were purified to homogeneity. Their molar mass, estimated by SDS-PAGE, were 21 and 24 kDa, respectively. Both enzymes are glycoproteins with 50 degrees C temperature optimum; optimum pH was 6.0-6.5 for xylanase I and 6.0 for xylanase II. At 50 degrees C xylanase I exhibited higher thermostability than xylanase II. Hg2+, Cu2+ and SDS were strong inhibitors, 1,4-dithiothreitol stimulated the reaction of both enzymes. Both xylanases are xylan-specific; kinetic parameters indicated higher efficiency in the hydrolysis of oat spelts xylan. In hydrolysis of this substrate, xylotriose, xylotetraose and larger xylooligosaccharides were released and hence the enzymes were classified as endoxylanases.

Molecular characteristics and transcription of the gene encoding a multifunctional alcohol dehydrogenase in relation to the deactivation of pyruvate formate-lyase in the ruminal bacterium Streptococcus bovis

To clarify the deactivation mechanism of pyruvate formate-lyase (PFL) and its role in the regulation of fermentation in Streptococcus bovis, the molecular properties and genetic expression of multifunctional alcohol dehydrogenase (ADHE) were investigated. S. bovis was found to have ADHE, which was deduced to consist of 872 amino acids with a molecular mass of 97.4 kDa. The ADHE was shown to harbor three enzyme activities: (1) alcohol dehydrogenase, (2) coenzyme-A-linked acetaldehyde dehydrogenase that catalyzes the conversion of acetyl-CoA to ethanol, and (3) PFL deactivase. Similar to Escherichia coli ADHE, S. bovis ADHE required Fe2+ for its activity. The gene encoding ADHE ( adhE) was shown to be monocistronic. The level of adhE mRNA changed in parallel with the mRNA levels of the genes encoding PFL (pfl) and PFL-activating enzyme (act) as the growth conditions changed, although these genes are independently transcribed. Synthesis of ADHE, PFL-activating enzyme, and PFL appears to be regulated concomitantly. Overexpression of ADHE did not cause a change in the formate-to-lactate ratio. It is conceivable that ADHE is not significantly involved in the reversible inactivation of active PFL under anoxic conditions. Partition of the flow from pyruvate appears to be mainly regulated by the activities of lactate dehydrogenase and PFL.

A chitinase with high activity toward partially N-acetylated chitosan from a new, moderately thermophilic, chitin-degrading bacterium, Ralstonia sp. A-471

A moderately thermophilic bacterium, strain A-471, capable of degrading chitin was isolated from a composting system of chitin-containing waste. Analysis of the 16S rDNA sequence revealed that the bacterium belongs to the genus Ralstonia. A thermostable chitinase A ( Ra-ChiA) was purified from culture fluid of the bacterium grown in colloidal chitin medium. Purification of the enzyme was achieved mainly by exploiting its binding to the colloidal chitin. The molecular mass of the enzyme was estimated to be 70 kDa and the isoelectric point approximately 4.7. N-terminal amino acid sequencing revealed a sequence of ADPYLKVAYYP, which had high homology (66% identity) with that of chitinase A1 from Bacillus circulans WL-12. The pH and temperature optima were determined to be 5.0 and 70 degrees C, respectively. The enzyme was classified as a retaining glycosyl hydrolase and was most active against partially N-acetylated chitosans. Its activities towards the partially N-acetylated chitosans, i.e. chitosan 7B, chitosan 8B, and chitosan 9B, were about 11-fold, 9-fold, and 5-fold higher than towards colloidal chitin, respectively. Ra-ChiA cleaved (GlcNAc)6 almost exclusively into (GlcNAc)2. Activation of Ra-ChiA was observed by the addition of 1 mM Cu2+, Mn2+, Ca2+, or Mg2+. Degradation of the partially N-acetylated chitosan produced oligosaccharides with a degree of polymerization ranging from 1-8; these are products that offer potential application for functional oligosaccharide production.

Magnesium-Dependent Ecto-ATP Diphosphohydrolase Activity in Herpetomonas muscarum muscarum

In the present work we characterized the ecto-ATP diphosphohydrolase activity of the trypanosomatid parasite Herpetomonas muscarum muscarum. This parasite hydrolyzed ATP at a rate of 15.52 nmol Pi/mg protein/min and this activity reached a maximum at pH 7.5. Classical inhibitors of acid phosphatases, such as sodium orthovanadate (NaVO3), sodium fluoride (NaF), and ammonium molybdate presented no effect on this activity. MgCl2, ZnCl2, and MnCl2 stimulated the ATP hydrolysis by H. m. muscarum. The ecto-ATPase activity was insensitive to oligomycin and sodium azide, two inhibitors of mitochondrial Mg-ATPase, bafilomycin A1, a V-ATPase inhibitor, ouabain, a Na(+)+K+-ATPase inhibitor and to levamizole, an inhibitor of alkaline phosphatase. An extracellular impermeant inhibitor 4,4'-diisothiocyanostylbene 2',2'-disulfonic acid (DIDS) and a inhibitor of some ecto-ATPases, suramin, which is also a competitive antagonist of P2-purinergic receptors, promoted a great inhibition on the ATP hydrolysis. This enzyme is able to hydrolysis ATP, ADP, UTP, and UDP, but not GTP, GDP, CTP, or CDP. ADP inhibited the enzymatic activity in a concentration dependent manner, reaching 70% inhibition.

Telomerase activity and telomerase reverse transciptase (TERT) expression in ameloblastomas

Telomerase activity is believed to be crucial for cell immortalization and cancerization, and is proven to be induced by c-myc protein. Telomerase reverse transcriptase (TERT) has been recently identified as a catalytic subunit of telomerase, whose expression is closely correlated with telomerase activity. We estimated telomerase activity by the telomeric repeat amplification protocol (TRAP) assay and examined the immunohistochemical expression of TERT and c-myc protein in 21 ameloblastoma tissues. All ameloblastoma samples were positive for telomerase activity, and TERT expression was detected in the nuclei of neoplastic cells but not in those of stromal cells. Numerous peripheral columnar or cuboidal cells, sporadic central polyhedral cells and some granular cells in ameloblastomas reacted with anti-TERT antibody. These results suggest that telomerase activity is associated with the oncogenesis or proliferative potential of odontogenic epithelium. The expression of c-myc protein showed a similar distribution pattern to that of TERT, suggesting that c-myc protein might induce telomerase activity in ameloblastomas.

Circadian regulation of uroguanylin and guanylin in the rat intestine

Uroguanylin (UGN) and guanylin (GN) are the endogenous intestinal ligands for guanylyl cyclase C (GC-C). We examined the circadian expression of UGN, GN, and GC-C in the jejunum, ileum, and proximal colon of young adult rats by Northern blot analyses. These assays revealed that UGN is more abundant in the proximal small intestine, whereas GN and GC-C are more abundant in the proximal colon. mRNA levels showed significant circadian variation for UGN (3- to 18-fold peak/trough difference), GN (2.1- to 2.8-fold peak/trough difference), and GC-C (3- to 5-fold peak/trough difference). The maximal abundance occurred in the dark period for all three mRNAs, although peak UGN and GN expression occurred later in the dark period in the jejunum relative to the ileum and colon. Immunoblot analyses using monospecific polyclonal antibodies against UGN and GN prohormones confirmed the regional and circadian variation detected by Northern assays. Thus the expression of these genes is regulated not only by histological position but also by circadian time.