Immobilization of glycoenzymes through carbohydrate side chains

Enzyme-linked immunosorbent assay with monoclonal and single-chain variable fragment antibodies selective to coplanar polychlorinated biphenyls

Coplanar polychlorinated biphenyls (Co-PCBs) consisting of non-ortho and mono-ortho-chlorinated PCBs are dioxin-like compounds and cause wide contamination in the environment. To monitor Co-PCB residues, it was attempted to establish an enzyme-linked immunosorbent assay (ELISA) with monoclonal and recombinant antibodies selective to Co-PCBs. When 3,3',5,5'-tetrachlorobiphenoxybutyric acid (PCBH)-keyhole limpet hemocyanin conjugate was immunized into mice, two monoclonal antibodies, Mab-0217 and Mab-4444, were obtained. 3,3',5,5'-Tetrachlorobiphenyl (PCB80) was determined with an IC(50) value of 2.6 and 0.46 ng mL(-1) in ELISA based on Mab-0217 and Mab-4444, respectively. Mab-4444 cross-reacted with Co-PCB congeners, except for PCB77 and PCB81. Mab-0217 reacted with PCB80 and cross-reacted with PCB111. A single-chain variable fragment (scFv) antibody derived from Mab-4444 was produced in recombinant Escherichia coli cells. The scFv antibody showed nearly the same sensitivity toward PCBH as the parent monoclonal antibody in ELISA. These results clearly suggested that Mab-4444 and its scFv antibodies were suitable for monitoring the representative congeners of Co-PCBs.

Immobilization of dextranase from Chaetomium erraticum

In order to facilitate the Co-Immobilization of dextransucrase and dextranase, various techniques for the immobilization of industrial endo-dextranase from Chaetomium erraticum (Novozymes A/S) were researched. Adsorption isotherms at various pH-values have been determined for bentonite (Montmorillonite), hydroxyapatite and Streamline DEAE. Using bentonite and hydroxyapatite, highest activity loads (12,000 Ug(-1); 2900 Ug(-1), respectively) can be achieved without a significant change of the apparent Michaelis-Menten constant K(M). For successful adsorption, enzyme to bentonite ratios greater than 0.4 (w/w) have to be used as lower ratios lead to 90% enzyme inactivation due to bentonite contact. In addition, covalent linkage using the activated oxiran carriers Eupergit C and Eupergit C250L as well as linkage with aminopropyl silica via metaperiodate activation of glycosyl moiety of dextranase are discussed. This is also the first report probing the structure of a matrix containing dextranase by use of substrate species with different molecular weights. From this we can observe a relationship between the porosity of Eupergit and dextran dependent activity. For the reactor concept using Co-Immobilisates, hydroxyapatite will be preferred to Eupergit because of its higher specific activity and dispersity.

Additional stabilization of stem bromelain coupled to a thermosensitive polymer by uniform orientation and using polyclonal antibodies

Stem bromelain was covalently coupled to a thermosensitive polymer of N-isopropylacrylamide (p(NIPAm)) either through the amino groups of the enzyme (randomly coupled) or via the lone oligosaccharide chain (uniformly coupled). The enzyme coupled via the oligosaccharide chain exhibited better access to the substrate casein as compared to the preparation in which the amino groups formed the point of contact between the enzyme and the polymer. Native bromelain exhibited a pH optimum of 8.0 and a broad pH-activity profile. The polymer-coupled preparations exhibited broader pH-activity profiles and shifting of pH optimum to 10.0 at 35 degrees C. At 25 degrees C, the shifting of pH optimum was observed for the randomly coupled enzyme only. The temperature-activity profiles of bromelain coupled to p(NIPAm) also showed appreciable broadening and the preparations retained greater fraction of maximum activity above the temperature optimum. The optimum temperature of the uniformly oriented preparation also rose to 70 degrees C. Inactivation rates of the polymer-coupled bromelain were remarkably low at 60 degrees C as compared to the native protease, and binding of antibromelain antibodies improved the resistance to inactivation of the polymer-coupled preparations. The cleavage patterns of hemoglobin and IgG by the native bromelain and the polymer-coupled preparations were comparable.

Immobilization and stabilization of invertase on Cajanus cajan lectin support

Use of lectins as ligands for the immobilization and stabilization of glycoenzymes has immense application in enzyme research and industry. But their widespread use could be limited by the high cost of their production. In the present study preparation of a novel and inexpensive lectin support for use in the immobilization of glycoenzymes containing mannose or glucose residues in their carbohydrate moiety has been described. Cajanus cajan lectin (CCL) coupled covalently to cyanogen bromide activated Seralose 4B could readily bind enzymes such as invertase, glucoamylase and glucose oxidase. The immobilized and glutaraldehyde crosslinked preparations of invertase exhibited high resistance to inactivation upon exposure to enhanced temperature, pH, denaturants and proteolysis. Binding of invertase to CCL-Seralose was however found to be readily reversible in the presence of 1.0 M methyl alpha-D mannopyranoside. In a laboratory scale column reactor the CCL-Seralose bound invertase was stable for a month and retained more than 80% of its initial activity even after 60 days of storage at 4 degrees C. CCL-Seralose bound invertase exhibited marked stability towards temperature, pH changes and denaturants suggesting its potential to be used as an excellent support for the immobilization of other glycoenzymes as well.

Bioaffinity based immobilization of enzymes

Procedures that utilize the affinities of biomolecules and ligands for the immobilization of enzymes are gaining increasing acceptance in the construction of sensitive enzyme-based analytical devices as well as for other applications. The strong affinity of polyclonal/monoclonal antibodies for specific enzymes and those of lectins for glycoenzymes bearing appropriate oligosaccharides have been generally employed for the purpose. Potential of affinity pairs like cellulose-cellulose binding domain bearing enzymes and immobilized metal ionsurface histidine bearing enzymes has also been recognised. The bioaffinity based immobilization procedures usually yield preparations exhibiting high catalytic activity and improved stability against denaturation. Bioaffinity based immobilizations are usually reversible facilitating the reuse of support matrix, orient the enzymes favourably and offer the possibility of enzyme immobilization directly from partially pure enzyme preparations or even cell lysates. Enzyme lacking innate ability to bind to various affinity supports can be made to bind to them by chemically or genetically linking the enzymes with appropriate polypeptides/domains like the cellulose binding domain, protein A, histidine-rich peptides, single chain antibodies, etc.

Bioaffinity layering: a novel strategy for the immobilization of large quantities of glycoenzymes

A simple strategy for increasing considerably the quantities of glycoenzymes immobilized on insoluble supports is described. The strategy that we call bioaffinity layering makes use of the multivalent nature of concanavalin A (Con A) and the multiple oligosaccharide chains of most glycoenzymes to build alternating lectin and glycoenzyme layers on a Sepharose matrix with precoupled Con A. Using this procedure, it was possible to increase the amounts of several glycoenzymes immobilized on Sepharose and 19.0 mg glucose oxidase could be associated with one ml Sepharose matrix after seven Con A/glucose oxidase incubation cycles. Bioaffinity layered preparations of glycoenzymes exhibited high activities as indicated by very high effectiveness factor (eta) values and those of glucose oxidase and invertase exhibited a layer-by-layer increase in thermostability. The sensitivity of a flow-through glucose monitoring cartridge integrated into a flow injection analysis (FIA) system was enhanced significantly by increasing the amount of immobilized glucose oxidase via bioaffinity layering. A cartridge bearing six layers of glucose oxidase on Sepharose support was used effectively and repeatedly for analysis of medium glucose concentration during a fed-batch cultivation of the yeast Saccharomyces cerevisiae.

Two-dimensional paracrystalline glycoprotein S-layers as a novel matrix for the immobilization of human IgG and their use as microparticles in immunoassays

In the present study, cup-shaped 1-3 microns large cell wall fragments from Thermoanaerobacter thermohydrosulfuricus L111-69 covered with a hexagonal S-layer lattice composed of glycoprotein subunits were shown to act as a matrix for the immobilization of human IgG. After cross-linking the S-layer glycoprotein lattice with glutaraldehyde (S-layer microparticles), IgG was either bound to carbodiimide activated carboxyl groups from acidic amino acids from the protein moiety or to the carbohydrate chains activated with cyanogen bromide or oxidized with periodate. After determining the binding capacity of the S-layer lattice for human IgG, the orientation of the immobilized antibody molecules was investigated using anti-human IgG peroxidase conjugates with different specificity. Attachment of S-layer microparticles with covalently bound human IgG to microplates precoated with anti-human IgG of different specificity led to clear correlations between the amount of applied human IgG and the absorption values in the immunoassays. The steepest absorption curves were obtained when human IgG was bound to the carbohydrate chains exposed on the surface of the S-layer lattice. This confirmed that the location and the accessibility of the immobilized antibodies on S-layer microparticles is of major importance for the response in immunoassays. In addition to the high reproducibility of the amount of IgG which could be bound to the S-layer lattice and the high reproducibility of the absorption curves in the immunoassays, one major advantage of using cup-shaped S-layer microparticles can be seen in the considerable increase of the actual surface available for binding processes and immunological reactions.

Studies on oriented and reversible immobilization of glycoprotein using novel boronate affinity gel

The authors have previously synthesized a novel boronate affinity ligand, catechol [2-(diethylamino)carbonyl-4-bromomethyl]phenylboronate. When this ligand was coupled to cellulose beads, it bound horseradish peroxidase (HRP), a glycoprotein, at pH 7.0. In comparison, commercial m-aminophenylboronic acid-agarose did not bind HRP below pH 8.0. HRP was immobilized in an oriented and reversible fashion using this gel. The immobilized enzyme retained 90.12 per cent of its original activity, probably due to its attachment via the carbohydrate moiety of the enzyme. After repeated use, the activity remaining on the new gel was twice as high as that on conventional m-aminophenylboronic acid-agarose. The column was regenerated easily by washing with dilute acid because of reversibility of the boronate glycol bond.

Enzyme immobilization on a low-cost magnetic support: kinetic studies on immobilized and coimmobilized glucose oxidase and glucoamylase

Glucose oxidase (GOx) and glucoamylase (GA) were immobilized and coimmobilized through their carbohydrate moieties onto polyethyleneimine-coated magnetite crosslinked with glutaraldehyde and derivatized with adipic dihydrazide. The carbohydrates were oxidized with sodium periodate, and at optimal concentration, their Vm increased up to 18% for GOx and up to 16% for GA. After immobilization, a remaining activity as high as 88% and 70% for GA with maltose and maltodextrin respectively as substrates was obtained, independently of the particle loading. On the contrary, the remaining activity of GOx strongly decreased at high particle loading. Nevertheless, half of its initial activity was recovered at low loading and was not significantly affected when GA was coimmobilized by saturating the reactive groups left on the particle. The Vm of both immobilized enzymes was improved by crosslinking their carbohydrates with adipic dihydrazide, a treatment which allows further coimmobilization of the other enzyme on a second layer.

Galactosylation as a tool for the stabilization and immobilization of proteins

This paper presents a brief overview of the role that the carbohydrate moieties of biologically active glycoproteins play in the stabilization and oriented immobilization of these proteins on solid supports. The synthetic galactosylation of hydrophobic areas or their surroundings on the protein surface improves the structural stability of native proteins against inactivation by the interaction of water with hydrophobic clusters. The lowering of the degree solvation of tyrosine residues in galactosylated trypsin and the model substance N-carbobenzoxy-L-glutamyl-L-tyrosine was proved by Raman spectroscopy. D-Galactose residues can be selectively oxidized, either with periodate or enzymatically, and the aldehyde groups thus formed are used for the immobilization of glycoproteins on solid supports with hydrazide groups under mild conditions.

Concanavalin A: a useful ligand for glycoenzyme immobilization--a review

Concanavalin A is finding increasing applications as a useful ligand in glycoenzyme immobilization. An attempt therefore, has been made to summarize the work available in the area. Glycoenzymes that are recalcitrant to immobilization procedures involving covalent coupling to solid supports can be immobilized in high yields by binding to matrices precoupled with concanavalin A. In addition, glycoenzymes associated with concanavalin A matrices usually exhibit high retention of activity and enhanced stability against various forms of inactivation. Binding of the glycoenzymes on the concanavalin A supports, being noncovalent, can be reversed by incubating the preparation with a high concentration of sugars/glycosides or at acidic pH. The association can be, however, rendered covalent by crosslinking the preparations with bifunctional reagents like glutaraldehyde. Crosslinking may be accompanied by further increase in stability, albeit at the expense of the loss of some enzyme activity. Several laboratory-size reactors containing concanavalin A matrix-bound glycoenzyme have been successfully operated for reasonably long durations with only small losses in catalytic activity. Insoluble glycoenzyme preparation can also be obtained by precipitating them from solution as concanavalin A complexes. Such complexes have small particle dimensions but can be successfully used in column reactors after a subsequent immobilization step. Insoluble concanavalin A-flocculates containing various microorganisms and glycoenzymes that successfully carry out multistep transformations have also been obtained by several investigators.

Targeted neuronal lesion induced by photosensitizing dyes

Free radical-induced phototoxicity mediated by laser irradiation was investigated in the rabbit facial nerve. Azure-C, mesoporphyrin, or the dye conjugated to the protein carrier horseradish peroxidase were injected into the levator alae nasi muscle. Two to 7 days after uptake and laser exposure, nerve sections showed varying degrees of cellular modifications including: severe membrane degradation and associated lipid peroxide granules, distended mitochondria, and mitochondrial loss. Immunoblots of homogenates from treated nerves revealed specific changes in neurofilament and myelin basic protein. The site specific damage produced in vivo by photosensitizing dye resembles abnormalities in aging neurons and in Batten's disease, both hypothesized to be cases of free radical-peroxidation reactions. These reactions differ from those found in transection and crush lesions.

Hydrazido-derivatized supports in affinity chromatography

Many chemistries have been developed for the immobilization of ligands onto insoluble matrices for subsequent use in affinity systems. One such chemistry which has received little attention involves the use of hydrazido-derivatized solid supports. Hydrazine derivatives are strong nucleophiles which will react with a number of functional groups including aldehydes which may be generated on the oligosaccharide moieties of glycoconjugates by specific oxidation reactions. This paper presents a brief overview of the chemistries involved and the uses of hydrazido-derivatized solid supports for the site-directed immobilization of glycoconjugates. Specific examples from the literature on the uses of affinity matrices prepared by this method are cited.

Preparation and properties of RNase T2 immobilized on concanavalin A-sepharose

Partially purified RNase T2 (EC 2.7.7.17) from Aspergillus oryzae was bound through its carbohydrate moiety to Concanavalin A-Sepharose. The retention of activity was high, ranging from 70% at low enzyme load to approximately 9% at high enzyme load. Though there was no change in the pH and temperature optima, the pH stability and the Km decreased after immobilization. Compared to the soluble enzyme, the immobilized RNase T2 showed enhanced temperature stability and more resistance to metal ions. Both soluble and immobilized enzymes were stable to 8 M urea. On repeated use, the bound enzyme retained more than 60% of its initial activity after six cycles.

Influence of lectin concentration on the catalytic properties of S1 nuclease bound to Concanavalin A-sepharose

Partially purified S1 nuclease was bound through its carbohydrate moiety to Con A-Sepharose containing increasing amounts of lectin. The retention of activity was high, varying essentially from 75% on the "low lectin" matrix (1 mg Con A/mL of Sepharose), to no detectable activity on the "high lectin" matrix (8 mg Con A/mL of Sepharose). However, approximately 50% activity could be restored in "high lectin" matrix when the coupling was carried out in the presence of glucose, suggesting that the loss of activity on the "high lectin" matrix is caused by conformational changes brought about by the multiple attachment of the enzyme to the matrix. Interaction of Con A with S1 nuclease was used to predict the nature of carbohydrate moiety and its location with respect to the active site of the enzyme. Immobilization resulted in an increase in the optimum temperature, pH, and temperature stabilities, but it did not affect the pH optimum. A marginal increase in the apparent Km was observed. The bound enzyme also showed enhanced stability toward 8 M urea. On repeated use, the bound enzyme retained more than 80% of its initial activity after 6 cycles. These results are discussed taking into consideration the factors affecting immobilized enzymes. In addition, the potential use of immobilized S1 nuclease as an analytical tool is discussed.

A Coomassie blue-binding assay for the microquantitation of immobilized proteins

A sensitive assay procedure for the determination of microgram quantities of immobilized proteins is described. The procedure is based on the property of Coomassie blue G-250 to bind strongly yet reversibly to proteins. The assay involves incubation of the immobilized protein with a solution containing 0.1% Coomassie blue, 10% acetic acid, and 25% isopropyl alcohol in distilled water at room temperature followed by washing off of the unbound dye. The protein-bound dye is eluted with methanolic NaOH, acidified, and the absorbance is measured at 605 nm. The assay is highly reproducible and several proteins immobilized on various matrices could be conveniently assayed. Protein values determined by the dye-binding assay showed good agreement with those obtained by other procedures.

Conformational studies of soluble and immobilized frog epidermis tyrosinase by fluorescence

Fluorescence spectra and soluble quenching of intrinsic protein fluorescence were used as indexes of conformational changes suffered by frog epidermis tyrosinase. The activation process and the immobilization of the enzyme involving either free amino groups or its carbohydrate moiety were studied. The conformational changes resulting from denaturation of each one of the protein derivatives, as well as the effect of active center copper extraction, were followed by fluorescence studies. The results showed that: both activation and immobilization were accompanied by conformational changes of the protein leading to more unfolded states; neither enzyme nor immobilized enzyme were fully unfolded upon denaturation although enzymic activity was lost; the enzyme immobilized through its carbohydrate moiety was more unfolded upon denaturation than the enzyme immobilized through amino groups, thus pointing to a higher conformational stabilization in the last situation; and that tryptophyl residues moved to a localization near the active site upon activation.

Stepwise immobilization of proteins via their glycosylation

Glycosyl derivatives of bovine serum albumin in which the glycosyl residue is represented by mono- or disaccharide can be, after periodate oxidation, coupled to polyhydrazides having a macroporous matrix (cross-linked polyacrylamide, bead cellulose). The amount of the linked neoglycoprotein depends not only on the physical structure of the matrix but also on the degree of its substitution with hydrazide groups and on the type and concentration of glycosyl residue in the neoglycoprotein. A high degree of substitution as well as the presence of the D-galactosyl unit both play a positive role. Owing to the fact that the glucosyl unit in disaccharide residues (cellobiosyl, lactosyl) also contributes positively to spacer properties, in the monolactosyl derivative of albumin exhibits good binding properties towards macroporous polyhydrazides. While the high sugar-containing conjugates of glycosyl derivatives of albumin with polyhydrazides are stable for two weeks at pH 6-9, the conjugates of the monolactosyl derivative of albumin can only be stored at pH 7.5. The binding site of albumin immobilization is considered.