High-performance affinity chromatography of plasmin and plasminogen on a hydrophilic vinyl-polymer gel coupled with p-aminobenzamidine

Separation of proteases: old and new approaches

All methods of protein separations can be applied to proteases. Some emphasis is put in this review on a powerful technique specific to proteases purification: cyclic peptide antibiotics may be seen as general affinity ligands for proteases. Also, some examples of affinity chromatography of proteases on ligands with narrower specificity are given. The special interest of hydrophobic interaction chromatography for proteases purification is discussed. The merits of immobilized dye chromatography for proteases purification and the interest in empirically screening many immobilized dyes, as well as several eluents are discussed.

Trypsin and affinity chromatography

Affinity adsorbents for trypsin which were prepared by immobilizing product-type ligands, that is, peptides having C-terminal arginine, proved to be effective not only for preparative purposes but also for basic research on molecular recognition. The properties of the binding site of trypsin were revealed by chromatographic experiments. Quantitative analysis based on the theory of frontal affinity chromatography proved to be extremely effective. As an extension of the product-type ligands, peptide argininals were also used and information on the mechanism of action of these inhibitors was obtained. Anhydrotrypsin, which lost the hydroxyl group of Ser183, was found to gain increased binding ability for product-type compounds. This inactivated enzyme was also used as an immobilized ligand and the unique affinity adsorbent thus prepared proved to be extremely effective for the separation of peptides and recombinant proteins based on their C-terminal structures. High-performance affinity chromatography of trypsin and related enzymes using a polymer-based support was also developed.

Immobilized urokinase column as part of a specific detection system for plasminogen species separated by high-performance affinity chromatography

Immobilized urokinase was used as part of a post-column reactor for the specific detection of human plasminogen species which were fractionated using a high-performance affinity column. After on-line activation of each peak, plasmin activity was measured by mixing the eluate with a specific fluorogenic substrate and the product was detected by a fluorescence monitor. This detection system gave linear calibration graphs for both purified plasminogens (0.1-50 micrograms) and plasminogens contained in plasma (25-100 microliters). Relative standard deviations for the determination of plasminogens in plasma were 6.1-6.6% (n = 12), showing good reproducibility. The detection limit was as low as 0.1 micrograms of plasminogen. Immobilized urokinase was very stable and no appreciable decrease in activity was found after 100 cycles of operation. In combination with an immobilized benzamidine column, this system made it possible to separate and detect Glu-plasminogen and Lys-plasminogen contained in human plasma samples as small as 100 microliters without any pretreatment.

Progress in affinophoresis

The use of polyionic polymers as mobile affinity matrices in electrophoresis has led to the development of a specific separation method for biological substances, affinophoresis. The conjugate of a polyionic polymer and an affinity ligand is called an affinophore. Electrophoresis of proteins in the presence of an affinophore results in a change in the mobility of a specific protein due to the difference between the mobility of the protein and that of the protein-affinophore complex. Polylysine is useful as a base polymer of affinophores and has been used successfully as an anionic matrix after succinylation. Affinophoresis of proteases, lectins and antibodies has been carried out in agarose gel and the mobility of the protein having affinity to each ligand was specifically changed. Two-dimensional affinophoresis, in which an affinophore was included only in the second-dimensional electrophoresis, was effective for the separation of the components of a complex mixture of proteins even if the change of mobility was not large. Red blood cells were successively treated with homologous antiserum, biotinylated second antibody, avidin and biotinylated succinylpolylysine as an affinophore. Specific acceleration of the homologous cells to the antiserum was observed even when the affinophoresis was applied to mixed red blood cells from different species.

High-performance liquid affinity chromatography with phenylboronic acid, benzamidine, tri-L-alanine, and concanavalin A immobilized on 3-isothiocyanatopropyltriethoxysilane-activated nonporous monodisperse silicas

Nonporous, microparticulate, monodisperse silicas with particle diameters between 0.7 and 2.1 microns are introduced as stationary phases in high-performance affinity chromatography. The immobilization of m-aminophenylboronic acid, p-aminobenzamidine, tri-L-alanine, and concanavalin A onto these silicas was successfully achieved using 3-isothiocyanatopropyl-triethoxysilane as an activation reagent. Immobilized phenylboronic acid was applied to the isolation of nucleosides, nucleotides, and glycoprotein hormones such as bovine follicotropin and human chorionic gonadotropin, while immobilized benzamidine was employed for the isolation of the serine proteases thrombin and trypsin, immobilized tri-L-alanine for the separation of pig pancreatic elastase and human leukocyte elastase, and immobilized concanavalin A for the isolation of horseradish peroxidase. In all affinity chromatographic systems studied, the nonporous monodisperse silicas showed improved chromatographic performance compared to results obtained with porous silica supports using identical activation and immobilization procedures. Furthermore, frontal analysis was used as a method to evaluate the influence of experimental parameters on biological activity and accessible ligand densities. Only minor changes in bioactivity were found with the nonporous affinity supports, where accessibilities were typically higher than ca. 60%. The immobilization of affinity ligands onto porous supports as used in this and associated papers thus represents a successful general procedure for the preparation of stable matrices with fast kinetics for use in high-performance affinity chromatography.

Analysis of human glutamyl- and lysylplasminogen by high-performance affinity chromatography

An analytical system for the fibrinolytic system in the blood is described, based on high-performance affinity chromatography and a newly devised specific proenzyme detection procedure. Plasminogen subspecies in human plasma without any pretreatment (less than 100 microliters) were specifically separated on an high-performance affinity column. For detection they were continuously activated by urokinase, and their elution profile was determined by assay of the plasmin activity using a specific fluorogenic substrate. Preliminary data on plasma from a patient are presented.

Combination of high-performance affinity chromatography and specific detection of proenzyme applicable to the analysis of the fibrinolytic system of human plasma

A procedure for the analysis of the fibrinolytic system in human blood was devised by combining high-performance affinity chromatography (HPAC) and specific detection of proenzyme. Components of the fibrinolytic system were separated by HPAC using Asahipak GS gel coupled with p-aminobenzamidine, and they were specifically detected by means of an on-line enzyme assay system. This system made it possible to quantitate not only Glu-plasminogen (Glu-Plg) but also Lys-plasminogen (Lys-Plg) in human plasma in a short time without pre-treatment. The effect of urokinase on the state of components of the fibrinolytic system in blood was studied. It was clearly shown that Lys-Plg is more susceptible to activation by urokinase than Glu-Plg (both in vitro and in vivo).

Separation of human Glu-plasminogen, Lys-plasminogen and plasmin by high-performance affinity chromatography on Asahipak GS gel coupled with p-aminobenzamidine

Human Glu-plasminogen, Lys-plasminogen and plasmin were effectively separated by high-performance affinity chromatography. The affinity adsorbent was prepared by using a micro-particulate polyvinyl alcohol gel (Asahipak GS-gel) as the supporting material and p-aminobenzamidine as the specific ligand. All of the active enzyme and proenzymes were adsorbed. Glu-plasminogen was eluted by changing the pH of the eluent and Lys-plasminogen by using an eluent containing 6-amino-hexanoic acid. This affinity adsorbent recognized the difference between these proenzyme species. For the elution of plasmin, addition of urea was necessary. Plasmin may have been adsorbed through a two-site interaction with the adsorbent. All proteins were eluted as sharp peaks and the time required for one cycle was about 1 h. Fluorimetric detection of eluted protein and on-line assay of enzyme activity using a fluorigenic substrate made it possible to analyse microgram amounts of proteins specifically.

High-performance affinity chromatography of trypsins on Asahipak GS-gel coupled with p-aminobenzamidine

An adsorbent for high-performance affinity chromatography of trypsins was prepared, based on a micro-particulate polyvinyl alcohol gel for high-performance liquid chromatography, Asahipak GS-gel. After the hydroxyl groups had been activated with 1,1'-carbonyldiimidazole, 6-aminohexanoic acid was coupled as a spacer, then p-aminobenzamidine, a specific ligand for trypsin-family enzymes, was immobilized on the spacer. Fluorometric detection of eluted protein and on-line assay of enzyme activity using a fluorogenic substrate, peptidylmethylcoumarylamide, made it possible to attain very high sensitivity. Microgram amounts of bovine trypsin and Streptomyces griseus trypsin could easily be analyzed in a short time (less than 1 h).