Fluorometric determination of mucin-type glycoproteins by the galactose oxidase-peroxidase method

Optimizing Wound Healing: Examining the Influence of Biopolymers Through a Comprehensive Review of Nanohydrogel-Embedded Nanoparticles in Advancing Regenerative Medicine

Nanohydrogel wound healing refers to the use of nanotechnology-based hydrogel materials to promote the healing of wounds. Hydrogel dressings are made up of a three-dimensional network of hydrophilic polymers that can absorb and retain large amounts of water or other fluids. Nanohydrogels take this concept further by incorporating nanoscale particles or structures into the hydrogel matrix. These nanoparticles can be made of various materials, such as silver, zinc oxide, or nanoparticles derived from natural substances like chitosan. The inclusion of nanoparticles can provide additional properties and benefits to the hydrogel dressings. Nanohydrogels can be designed to release bioactive substances, such as growth factors or drugs, in a controlled manner. This allows for targeted delivery of therapeutics to the wound site, promoting healing and reducing inflammation. Nanoparticles can reinforce the structure of hydrogels, improving their mechanical strength and stability. Nanohydrogels often incorporate antimicrobial nanoparticles, such as silver or zinc oxide. These nanoparticles have shown effective antimicrobial activity against a wide range of bacteria, fungi, and other pathogens. By incorporating them into hydrogel dressings, nanohydrogels can help prevent or reduce the risk of infection in wounds. Nanohydrogels can be designed to encapsulate and release bioactive substances, such as growth factors, peptides, or drugs, in a controlled and sustained manner. This targeted delivery of therapeutic agents promotes wound healing by facilitating cell proliferation, reducing inflammation, and supporting tissue regeneration. The unique properties of nanohydrogels, including their ability to maintain a moist environment and deliver bioactive agents, can help accelerate the wound healing process. By creating an optimal environment for cell growth and tissue repair, nanohydrogels can promote faster and more efficient healing of wounds.

Effects of temperature and glycerol and methanol-feeding profiles on the production of recombinant galactose oxidase in Pichia pastoris

Optimization of protein production from methanol-induced Pichia pastoris cultures is necessary to ensure high productivity rates and high yields of recombinant proteins. We investigated the effects of temperature and different linear or exponential methanol-feeding rates on the production of recombinant Fusarium graminearum galactose oxidase (EC 1.1.3.9) in a P. pastoris Mut⁺ strain, under regulation of the AOX1 promoter. We found that low exponential methanol feeding led to 1.5-fold higher volumetric productivity compared to high exponential feeding rates. The duration of glycerol feeding did not affect the subsequent product yield, but longer glycerol feeding led to higher initial biomass concentration, which would reduce the oxygen demand and generate less heat during induction. A linear and a low exponential feeding profile led to productivities in the same range, but the latter was characterized by intense fluctuations in the titers of galactose oxidase and total protein. An exponential feeding profile that has been adapted to the apparent biomass concentration results in more stable cultures, but the concentration of recombinant protein is in the same range as when constant methanol feeding is employed. © 2014 The Authors Biotechnology Progress published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers Biotechnol. Prog., 30:728–735, 2014

Assembly, postsynthetic modification and hepatocyte targeting by multiantennary, galactosylated soft structures

Enzyme modifiable, hollow self-assembled structures offer an excellent scope for multiantennary delivery vectors.

Purification and characterization of a new L-methioninase from solid cultures of Aspergillus flavipes

L-Methioninase was purified to electrophoretic homogeneity from cultures of Aspergillus flavipes using anion-exchange and gel filtration chromatography by 12.1 fold compared to the crude enzyme preparation. The purified enzyme had a molecular mass of 47 kDa under denaturing conditions and an isoelectric point of 5.8 with no structural glycosyl residues. The enzyme had optimum activity at pH 7.8 and pH stability from 6.8-8.0 at 35°C. The enzyme appeared to be catalytically stable below 40°C. The enzyme activity was strongly inhibited by DL-propargylglycine, hydroxylamine, PMSF, 2-mercaptoethanol, Hg(+), Cu(2+), and Fe(2+), with slight inhibition by Triton X-(100). A flavipes L-methioninase has a higher catalytic affinity towards L-methionine (Km, 6.5 mM and Kcat, 14.1 S(-1)) followed by a relative demethiolating activity to L-homo-cysteine (Km, 12 mM and Kcat, 9.3 S(-1)). The enzyme has two absorption maxima at 280 and 420 nm, typical of other PLP-enzymes. Apo-L-methioninase has the ability to reconstitute its structural catalytic state completely upon addition of 0.15 mM PLP. L-Methioninase has neither an appreciable effect on liver function, platelet aggregation, nor hemolysis of human blood. The purified L-methioninase from solid cultures of A. flavipes displayed unique biochemical and catalytic properties over the currently applied Pseudomonad enzyme.

A comparative summary of expression systems for the recombinant production of galactose oxidase

BACKGROUND

The microbes Escherichia coli and Pichia pastoris are convenient prokaryotic and eukaryotic hosts, respectively, for the recombinant production of proteins at laboratory scales. A comparative study was performed to evaluate a range of constructs and process parameters for the heterologous intra- and extracellular expression of genes encoding the industrially relevant enzyme galactose 6-oxidase (EC 1.1.3.9) from the fungus Fusarium graminearum. In particular, the wild-type galox gene from F. graminearum, an optimized variant for E. coli and a codon-optimized gene for P. pastoris were expressed without the native pro-sequence, but with a His-tag either at the N- or the C-terminus of the enzyme.

RESULTS

The intracellular expression of a codon-optimized gene with an N-terminal His10-tag in E. coli, using the pET16b+ vector and BL21DE3 cells, resulted in a volumetric productivity of 180 U·L-1·h-1. The intracellular expression of the wild-type gene from F. graminearum, using the pPIC3.5 vector and the P. pastoris strain GS115, was poor, resulting in a volumetric productivity of 120 U·L-1·h-1. Furthermore, this system did not tolerate an N-terminal His10-tag, thus rendering isolation of the enzyme from the complicated mixture difficult. The highest volumetric productivity (610 U·L-1·h-1) was achieved when the wild-type gene from F. graminearum was expressed extracellularly in the P. pastoris strain SMD1168H using the pPICZα-system. A C-terminal His6-tag did not significantly affect the production of the enzyme, thus enabling simple purification by immobilized metal ion affinity chromatography. Notably, codon-optimisation of the galox gene for expression in P. pastoris did not result in a higher product yield (g protein·L-1 culture). Effective activation of the enzyme to generate the active-site radical copper complex could be equally well achieved by addition of CuSO4 directly in the culture medium or post-harvest.

CONCLUSIONS

The results indicate that intracellular production in E. coli and extracellular production in P. pastoris comprise a complementary pair of systems for the production of GalOx. The prokaryotic host is favored for high-throughput screening, for example in the development of improved enzymes, while the yeast system is ideal for production scale-up for enzyme applications.

Continuous nonradioactive method for screening trypanosomal trans-sialidase activity and its inhibitors

Trypanosoma cruzi, the agent of American trypanosomiasis is unable to synthesize sialic acid (SA). Instead of using the corresponding nucleotide sugar as donor of the monosaccharide, the transfer occurs from alpha-2,3-linked SA in the host sialoglycoconjugates to terminal beta-galactopyranosyl units of the parasite mucins. For that purpose, T. cruzi expresses a glycosylphosphatidylinositol-anchored trans-sialidase (TcTS) that is shed into the milieu, being detected in the blood during the acute phase of the infection. The essential role of TcTS in infection and the absence of a similar activity in mammals make this enzyme an attractive target for the development of alternative chemotherapies. However, there is no effective inhibitor toward this enzyme. In vitro, 3'-sialyllactose (SL) as donor and radioactive lactose as acceptor substrate are widely used to measure TcTS activity. The radioactive sialylated product is then isolated by anion exchange chromatography and measured. Here we describe a new nonradioactive assay using SL or fetuin as donor and benzyl beta-d-Fuc-(1-->6)-alpha-d-GlcNAc (1) as acceptor. Disaccharide 1 was easily synthesized by regioselective glycosylation of benzyl alpha-d-GlcNAc with tetra-O-benzoyl-d-fucose followed by debenzoylation. Compound 1 lacks the hydroxyl group at C-6 of the acceptor galactose and therefore is not a substrate for galactose oxidase. Our method relies on the specific quantification of terminal galactose produced by trans-sialylation from the donor to the 6-deoxy-galactose (D-Fuc) unit of 1 by a spectrophotometric galactose oxidase assay. This method may also discriminate sialidase and trans-sialylation activities by running the assay in the absence of acceptor 1.

Galactose oxidase action on galactose containing glycolipids--a fluorescence method

Features that alter the glycolipid sugar headgroup accessibility at the membrane interface have been studied in bilayer lipid model vesicles using a fluorescence technique with the enzyme galactose oxidase. The effects on oxidation caused by variation in the hydrophobic moiety of galactosylceramide or the membrane environment for galactosylceramide, monogalactosyldiacylglycerol and digalactosyldiacylglycerol were studied. For this study we combined the galactose oxidase method for determining the oxidizability of galactose containing glycolipids, and the fluorescence method for determining enzymatic hydrogen peroxide production. Exposed galactose residues with a free hydroxymethyl group at position 6 in the headgroup of glycolipids were oxidized with galactose oxidase and subsequently the resultant hydrogen peroxide was determined by a combination of horseradish peroxidase and 10-acetyl-3,7-dihydroxyphenoxazine (Amplex Red). Amplex Red reacts with hydrogen peroxide in the presence of horseradish peroxidase with a 1:1 stoichiometry to form resorufin. With this coupled enzyme approach it is also possible to determine the galactolipid transbilayer membrane distribution (inside-outside) in bilayer vesicles.

The protease-activated receptor-2 agonist induces gastric mucus secretion and mucosal cytoprotection

Protease-activated receptor-2 (PAR-2), a receptor activated by trypsin/tryptase, modulates smooth muscle tone and exocrine secretion in the salivary glands and pancreas. Given that PAR-2 is expressed throughout the gastrointestinal tract, we investigated effects of PAR-2 agonists on mucus secretion and gastric mucosal injury in the rat. PAR-2-activating peptides triggered secretion of mucus in the stomach, but not in the duodenum. This mucus secretion was abolished by pretreatment with capsaicin, which stimulates and ablates specific sensory neurons, but it was resistant to cyclo-oxygenase inhibition. In contrast, capsaicin treatment failed to block PAR-2-mediated secretion from the salivary glands. Intravenous calcitonin gene-related peptide (CGRP) and neurokinin A markedly elicited gastric mucus secretion, as did substance P to a lesser extent. Specific antagonists of the CGRP1 and NK2, but not the NK1, receptors inhibited PAR-2-mediated mucus secretion. Pretreatment with the PAR-2 agonist strongly prevented gastric injury caused by HCl-ethanol or indomethacin. Thus, PAR-2 activation triggers the cytoprotective secretion of gastric mucus by stimulating the release of CGRP and tachykinins from sensory neurons. In contrast, the PAR-2-mediated salivary exocrine secretion appears to be independent of capsaicin-sensitive sensory neurons.