An assessment of nonspecific adsorption to Eudragit S-100 during affinity precipitation

The problem of nonspecific adsorption to the reversibly soluble-insoluble polymers is of considerable importance in the design of an affinity precipitation protocol. It was seen that activation and coupling of the affinity ligand to the polymer changes the nature of the polymer surface in a significant fashion. The results with pure trypsin, partially purified trypsin preparation, and crude protein extract-containing protein inhibitors of trypsin and alpha-amylase and the reversibly soluble-insoluble polymer Eudragit S-100, show that nonspecific adsorption may not be a severe limitation in such systems.

Sequential precipitation with reversibly soluble insoluble polymers as a bioseparation strategy: purification of beta-glucosidase from Trichoderma longibrachiatum

Precipitation of proteins/enzymes with reversibly soluble-insoluble polymers is a simple approach which can be easily scaled up. It is shown here that considerable purification may be achieved if more than one polymer (chosen judiciously) is used in sequence for purification. The principle is illustrated with purification of beta-glucosidase from a commercial preparation of Trichoderma longibrachiatum. Precipitation with chitosan removed cellulase activity from the preparation with 4-fold purification and 99% recovery of beta-glucosidase activity in the supernatant. The treatment of the supernatant with Eudragit S-100 precipitated 98% of the enzyme activity. The two different elution procedures gave 82% recovery (with 14-fold purification) and 86% recovery (with 12-fold purification) of the enzyme activity from the precipitate. A low molecular weight protein still present in these preparations could be removed by gel filtration. This finally yielded an electrophoretically homogeneous enzyme with 74% recovery and 29-fold purification.

Immobilization of Aspergillus niger xylanase on magnetic latex beads

Xylanase from Pectinex 3XL was purified 70-fold by precipitation with an enteric polymer, Eudragit S-100. The purified xylanase was immobilized on magnetic latex beads via carbodi-imide coupling. The immobilized preparation showed 80% of the total activity bound to the beads. The pH optimum remained unchanged at 6.0 and the Km increased from 0.25 g/100 ml (free enzyme) to 0.39 g/100 ml on immobilization. Immobilization resulted in significant thermal stability at 60 degrees C. The time course of hydrolysis of xylan at 60 degrees C by free enzyme as well as immobilized enzyme was also studied.

Purification and characterization of an acid phosphatase from Arachis hypogaea

An acid phosphatase from Arachis hypogaea (peanuts) has been purified. The electrophoretically homogeneous enzyme preparation is free of any phophodiesterase activity. The enzyme has a molecular weight of 120,000. Among the various phosphomonoesters tested, p-nitrophenylphosphate was found to be its most effective substrate. The Km for p-nitrophenylphosphate was 1.21 mM at pH 5.0 and 25 degrees C. The enzyme was thermostable and did not loose activity after 1 hr at 50 degrees C.

Affinity precipitation of trypsin with soybean trypsin inhibitor linked Eudragit S-100

Soybean trypsin inhibitor linked to Eudragit S-100 was used for the affinity precipitation of trypsin. Polymer and ligand concentrations used in conjugate preparation showed remarkable effect on the trypsin recovery. Trypsin precipitation efficiency amounted to 89% and recovery was 74%. The final purification of relatively crude commercial trypsin resulted in 1.85-fold purification. The SDS-PAGE analysis indicated significant purification. The precipitated enzyme activity was around 96% and recovered enzyme activity was 83%.

An insoluble aggregate of commercially available bovine serum albumin shows antiproteolytic activity

Chemical aggregation of bovine serum albumin by extensive chemical crosslinking with glutaraldehyde yielded an insoluble protein preparation with significant antiproteolytic activity. This was presumably due to the presence of alpha 2-macroglobulin in bovine serum albumin preparations. Chemical crosslinking of bovine serum albumin under optimum conditions was found to increase its antitryptic activity by about four times. The results indicate that enhanced rigidity of alpha 2-macroglobulin structure increases its antitryptic activity.

Purification of endo-polygalacturonase by affinity precipitation using alginate

The precipitation of alginate by Ca2+ at pH 3.8 was found to occur concomitantly with the precipitation of endo-polygalacturonase from Aspergillus niger. Under optimum conditions, 92% of the enzyme activity was precipitated. The enzyme could be recovered from the precipitate by washing with 0.5 M NaCl/0.2 M Ca2+. All the precipitated endo-polygalacturonase activity could be recovered in this way. The enzyme thus obtained was purified 10-fold. A comparison of SDS/PAGE gel patterns of the crude preparation and enzyme purified by the affinity precipitation also showed a significant purification of the enzyme.

Effect of concanavalin A on the activity of acid and alkaline phosphatases

The effect of Concanavalin A on the activity of acid and alkaline phosphatases has been investigated. Both the glycoproteins were inhibited by Con A (about 30-40% with 4 mg final concentration in the reaction mixture of Con A). In case of the acid phosphatase, the addition of 1.0 M NaCl, instead of 0.5 M, stimulated the enzyme activity at low concentrations of Con A. The significance of the lectin effect on the stability of glycoenzymes and its implications in bioseparation and enzyme immobilization is briefly discussed.

Enzyme function in organic solvents

Enzyme catalysis in organic solvents is being increasingly used for a variety of applications. Of special interest are the cases in which the medium is predominantly non-aqueous and contains little water. A display of enzyme activity, even in anhydrous solvents (water less than 0.02% by vol.), perhaps reflects that the minimum necessity for water is for forming bonds with polar amino acids on the enzyme surface. The rigidity of enzyme structure at such low water content results in novel substrate specificities, pH memory and the possibility of techniques such as molecular imprinting. Limited data indicates that, while enhanced thermal stability invariably results, the optimum temperature for catalysis may not change. If true in general, this enhanced thermostability would have extremely limited benefits. Medium engineering and biocatalyst engineering are relevant techniques to improve the efficiency and stability of enzymes in such low water systems. Most promising, as part of the latter, is the technique of protein engineering. Finally, this review provides illustrations of applications of such systems in the diverse areas of organic synthesis, analysis and polymer chemistry.

Entrapment of proteins by aggregation within sephadex beads

When a protein is aggregated by chemical crosslinking inside Sephadex beads of appropriate pore size, it gets trapped inside the beads. The above approach was used for immobilization of beta-galactosidase, acid phosphatase, trypsin, and concanavalin A. It was found to be a simple, convenient, and fast method for immobilization of proteins.

Preparation of heteroenzyme conjugates: trypsin-chymotrypsin and trypsin-alkaline phosphatase

Hybrid enzymes which have two different enzyme activities linked together covalently may be useful reagents for various applications, such as the determination of complex biological structures. The present paper describes the preparation and purification of two such enzyme-enzyme conjugates, namely, trypsin-chymotrypsin and trypsin-alkaline phosphatase. Whereas the former has been prepared by using the well-known bifunctional reagent glutaraldehyde, the latter exploited the Schiff base formation between the oxidized carbohydrate moiety of alkaline phosphatase and the free amino groups of trypsin.

A colorimetric procedure to monitor the extent of crosslinking of proteins by bisimidoesters

Reaction of proteins with bisimidoesters is one of the popular crosslinking techniques. The extent of the reaction cannot be followed directly using the commonly used free amino group-determining reagents ninhydrin and 2,4,6-trinitrobenzene sulfonic acid since they react with bisimidoesters. However, we found that the extent of amidination of protein could be followed colorimetrically by using 1-fluoro-2,4-dinitrobenzene.

Crosslinking of concanavalin A with glutaraldehyde

Crosslinking of Concanavalin A with low concentrations of glutaraldehyde gives a mixture of products. A specific product having about 66% of the biological activity of the native molecule was characterized. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis showed the presence of monomers, dimers, trimers, tetramers, and a small amount of pentamers as products. The presence of alpha-methyl mannoside during crosslinking changed the nature of the products, yielding a product retaining 80% of the biological activity. The crosslinked products showed greater stability than the native molecule at alkaline pH. However, the greatest stability under alkaline conditions was shown by the native molecule itself where alpha-methyl mannoside was present.

A conjugate of trypsin and chymotrypsin

A heteroenzyme conjugate retaining activities of two component enzymes from trypsin and chymotrypsin was prepared using N-succinimidyl pyridyl dithiopropionate as crosslinking reagent. The conjugate bound to both trypsin and chymotrypsin affinity columns. Trypsin and chymotrypsin were linked in the ratio of 1:1 on mol basis. The conjugate, when treated with dimethyladipimidate, showed decreased autolysis of its trypsin component.

A crosslinked preparation of E. coli beta-D-galactosidase

beta-D-Galactosidase from E. Coli was crosslinked using glutaraldehyde and two bisimidoesters. With glutaraldehyde and dimethyl adipimidate (DMA), it is possible to obtain preparations having higher activity than the native enzyme. Glutaraldehyde and DMA gave preparations showing enhanced thermal stability. The preparation crosslinked with DMA, when used for continuous hydrolysis of lactose in milk, was found to be significantly better than the native enzyme.

Crosslinked concanavalin A-O-(diethylaminoethyl)-cellulose--an affinity medium for concanavalin A-interacting glycoproteins

When concanavalin A (Con A) is reacted with a low concentration of glutaraldehyde, the product formed strongly binds to DEAE-cellulose. Thus, the resultant material can be used as an affinity medium for those glycoproteins which interact with Con A. This affinity medium is easy to prepare, has a capacity comparable to that of similar commercially available affinity media, and is stable for up to at least 6 months.

o-Benzoquinone-a reagent for determining conformational differences in related proteins

OBQ reacts specifically with methionine residues of RNAase A at highly acidic pH. At pH 3, whereas RNAase A does not react, RNAase S, S-protein and S-peptide all react with OBQ. RNAase A derivatives in which some of the methionines have been initially modified at pH 1, further react with OBQ at pH 3. Thus, reaction with OBQ can be used to monitor structural transitions and conformational differences involving methionines in proteins.