Transition-state affinity chromatography of trypsin-like proteinases with dipeptidyl argininal ligands

Cysteinyl proteinases and their selective inactivation

The affinity-labeling of cysteinyl proteinases may now be carried out with a number of peptide-derived reagents with selectivity, particularly for reactions carried out in vitro. These reagents have been described with emphasis on their selectivity for cysteine proteinases and lack of action on serine proteinases, the most likely source of side reactions among proteinases. Perhaps a crucial feature of this selectivity is an enzyme-promoted activation due to initial formation of a hemiketal, which may destabilize the reagent. Prominent among the reagent types that have this class selectivity are the peptidyl diazomethyl ketones, the acyloxymethyl ketones, the peptidylmethyl sulfonium salts, and peptidyl oxides analogous to E-64. The need for specific inhibitors capable of inactivating the target enzyme in intact cells and animals is inevitably pushing the biochemical application of these inhibitors into more complex molecular environments where the possibilities of competing reactions are greatly increased. In dealing with the current state and potential developments for the in vivo use of affinity-labeling reagents of cysteine proteinases, the presently known variety of cysteinyl proteinases had to be considered. Therefore this chapter has, at the same time, attempted to survey these proteinases with respect to specificity and gene family. The continual discovery of new proteinases will increase the complexity of this picture. At present the lysosomal cysteine proteinases cathepsins B and L and the cytoplasmic calcium-dependent proteinases are reasonable goals for a fairly complete metabolic clarification. The ability of investigators to inactivate individual members of this family in vivo, possibly without complications due to concurrent inactivation of serine proteinases by improvements in reagent specificity, is increasing. Among the cysteine proteinases, at least those of the papain super family, hydrophobic interactions in the S2 and S3 subsites are important and some specificity has been achieved by taking advantage of topographical differences among members of this group. Some of this has probably involved surface differences removed from the regions involved in proteolytic action. The emerging cysteine proteinases include some which, in contrast to the papain family, have a pronounced specificity in S1 for the binding of basic side chains, familiar in the trypsin family of serine proteinases. At least a potential conflict with serine proteinases can be avoided by choice of a covalent bonding mechanism. The departing group region, has not been exploited. As a sole contributor to binding, this region may be rather limited as a source of specificity.(ABSTRACT TRUNCATED AT 400 WORDS)

Novel Peptidomimetic Cysteine Protease Inhibitors as Potential Antimalarial Agents

The synthesis of a new class of peptidomimetics 1a-j, based on a 1,4-benzodiazepine scaffold and on a C-terminal aspartyl aldehyde building block, is described. Compounds 1a-j provided significant inhibitory activity against falcipains 2A and 2B (FP-2A and FP-2B), two cysteine proteases from Plasmodium falciparum.

Current trends in molecular recognition and bioseparation

Molecular recognition guides the selective interaction of macromolecules with each other in essentially all biological processes. Perhaps the most impactful use of biomolecular recognition in separation science has been in affinity chromatography. The results of the last 26 years, since Cuatrecases, Wilchek and Anfinsen first reported the purification of staphylococcal nuclease, have validated the power of biomolecular specificity for purification. This power has stimulated an explosion of solid-phase ligand designs and affinity chromatographic applications. An ongoing case in point is the purification of recombinant proteins, which has been aided by engineering the proteins to contain Affinity-Tag sequences, such as hexa-histidine for metal-chelate separation and epitope sequence for separation by an immobilized monoclonal antibody. Tag technology can be adapted for plate assays and other solid-phase techniques. The advance of affinity chromatography also has stimulated immobilized ligand-based methods to characterize macromolecular recognition, including both chromatographic and optical biosensor methods. And, new methods such as phage display and other diversity library approaches continue to emerge to identify new recognition molecules of potential use as affinity ligands. Overall, it is tantalizing to envision a continued evolution of new affinity technologies which use the selectivity built into biomolecular recognition as a vehicle for purification, analysis, screening and other applications in separation sciences.

Preparation and evaluation of peptidic aspartyl hemiacetals as reversible inhibitors of interleukin-1 beta converting enzyme (ICE)

Aspartyl aldehyde, Ac-Tyr-Val-Ala-Asp-H 1 (L-709,049), has been reported to be a potent, reversible inhibitor of interleukin-1 beta converting enzyme (ICE) [Thornberry, N.A. et al. (1992) Nature (London) 356, 768-774]. In the context of our own work, we have developed a general synthetic approach to peptidic aspartyl aldehydes. Semicarbazone derivative, H-Asp(Ot-Bu)-Sc 4, was identified as a stable, masked aspartyl aldehyde equivalent. We have used 4 to synthesize a series of mono-, di- and tripeptide aldehydes, and multigram quantities of Ac-Tyr-Val-Ala-Asp-H 1, Ac-Tyr-Val-Lys-Asp-Sc 21 and Ac-Tyr-Val-Lys-Asp-H 2. Biological evaluation of these aspartyl aldehydes and derivatives suggests that the tripeptide scaffold, Z-Val-Ala-Asp, is a peptide scaffold that retains good potency and selectivity for ICE.

Affinity purification of proteinases by a combination of immobilized peptidyl aldehyde and semicarbazone

D-Phe-Phe-argininal semicarbazone and Tyr-Gly-Gly-Phe-Leu-Arg-argininal semicarbazone were prepared using the solution phase synthesis method and characterized by mass spectrometry and nuclear magnetic resonance spectroscopy. The tripeptide and heptapeptide semicarbazones were individually immobilized on affi-Gel 15 resulting in two affinity columns called S3 and S7, respectively. A third affinity column was obtained by hydrolysing the semicarbazone moiety in column S3 to aldehyde (column A3). Serine proteinases such as trypsin or rat plasma kallikrein almost quantitatively bind to either S3 or A3 affinity columns. Under optimized conditions, more than 97% of trypsin bound to both columns S3 and A3. At a lower ionic strength and higher pH, 80-85% of rat plasma kallikrein bound to the same columns. Elution of both enzymes was achieved using mild conditions at near neutral pH and in the presence of a small amount of denaturant. Both proteinases were identified and characterized by high-performance liquid chromatography, sodium dodecylsulphate polyacrylamide gel electrophoresis and by their substrate specificity and inhibition profiles. A single purification (six-to seven-fold) step using either column S3 or A3 allowed the preparation of pure trypsin from commercial sources. Starting from rat plasma partially purified by a phenyl boronate column, fractionation on the S3 column allowed approximately an 87-fold purification of rat plasma kallikrein. However, serial purification of rat plasma kallikrein on column S7 followed by column A3 resulted in a purification factor of about 455.

Quantification of peptide aldehyde ligands immobilized for the affinity chromatography of endopeptidases

A method is described for quantification of aldehyde and aldehyde semicarbazone groups attached to an insoluble matrix. Semicarbazones are converted to aldehydes, and the aldehydes are coupled with 4-phenylazoaniline. The excess reagent is washed off, and the remainder then displaced with salicylaldehyde. The quantity of the phenylazoaniline/salicylaldehyde adduct is determined spectrophotometrically, allowing the calculation of the amount of aldehyde or semicarbazone per unit volume of the matrix. Analyses by the new method show that four matrices offered commercially for this type of immobilization differ greatly in coupling capacity and stability of the conjugate under conditions of affinity chromatography.

Design of novel affinity adsorbents for the purification of trypsin-like proteases

A number of ligands for the selective purification by affinity chromatography of the trypsin-like protease, porcine pancreatic kallikrein, were designed de novo by computer-aided molecular design. The ligands were designed to mimic the side-chains of a number of arginyl dipeptides and included a benzamidine moiety substituted on a triazine ring. The ligands displayed inhibitory activities against pancreatic kallikrein which mirrored the specificity constants of the dipeptides they were designed to mimic. The ligand with the highest affinity for the enzyme, an analogue of a Phe-Arg dipeptide, when immobilized to Sepharose CL-4B via a hexamethylene spacer arm, purified pancreatic kallikrein 110-fold in one step from a crude pancreatic acetone extract.

Syntheses of argininal semicarbazone containing peptides and their applications in the affinity chromatography of serine proteinases

Eight argininal semicarbazone containing peptides prepared by liquid phase synthesis were all found to be reversible inhibitors of model serine proteinases including trypsin and plasma kallikrein (PK). Among the peptides tested, those having a Lys residue at position P2 displayed the maximum binding potency towards PK. One of the peptides, Leu-enkephalin-argininal semicarbazone, a comparatively weak inhibitor, was chosen in order to develop an affinity-based purification protocol for PK. The affinity column was prepared by covalent attachment of the NH2-terminal moiety of the peptidyl semicarbazone to a solid-phase matrix bearing a spacer group. For efficient binding of PK, it was found necessary to optimize parameters like the concentration of inhibitor linked to the solid matrix, the ionic strength of the buffer used, the temperature and the pH. The majority of the bound enzyme could be recovered following elution with guanidine hydrochloride or benzamidine hydrochloride in a high salt buffer at pH 6.0. The usefulness of the affinity procedure towards the purification of other serine proteinases is also discussed.

Affinity purification of tissue plasminogen activator using transition-state analogues

The search for a simple affinity ligand to purify tissue plasminogen activator (tPA) was facilitated by a solid-phase synthesis approach. A large variety of tripeptide ligands containing argininal were synthesized on agarose gels containing a spacer with carboxy terminal. The immobilized ligands were easy to test with urokinase, and tPA. While a number of sequence combinations showed initial binding by tPA, only a few resulted in tight binding corresponding to a hemiacetal linkage with the active site serine. Hydrophobic residues, especially aromatics, flanking the N-side of argininal gave rise to ligands which were bound strongly by tPA. A gel containing D-Phe-D-Phe-Argal (an aldehyde derivative of arginine) was very effective in purifying tPA derived from cell culture media at small scale (milligrams) and at large (multi-grams).

[Purification of human thrombin by affinity chromatography for its use in preparations for biological coagulation]

Biological glue is obtained by mixing different specific plasma proteins including a serine protease, thrombin. Surprisingly at present the thrombin used in such a mixture is from equine or bovine origin while all other components are from human. In this paper we described a particular efficient and specific chromatographic method for the purification of human thrombin usable as a serine protease in the preparation of biological glue. A pure and active thrombin is obtained from a plasma fraction after adsorption on benzamidine-Spherodex followed by an elution with non specific (sodium chloride gradient) or biospecific competitors (arginine methylester or benzamidine). The obtained thrombin with a yield close to 80% and a purification factor close to 160, showed good properties in the replacement of animal thrombin in the condition of biological glue.

Biospecific interactions: their quantitative characterization and use for solute purification

Biospecificity is due largely to the formation and dissociation of non-covalent complexes between small molecules and macromolecules, or between two macromolecules. The first part of this review is concerned with the use of such biospecificity in the fractionation and identification of solutes. Major emphasis is given to affinity chromatography, especially in regard to the practical considerations inherent in an experimental situation and to the wide range of specific interactions that can be utilized. The second part of the review considers the quantitative characterization of biospecific complex formation. The merits of frontal gel chromatography, electrophoretic methods and affinity chromatography are discussed, and special consideration is given to the effects of ligand and/or acceptor multivalency because of its relevance to many biospecific interactions. Finally attention is drawn to the feasibility of employing quantitative affinity chromatographic theory for the determination of association constants for antigen-antibody systems by radioimmunoassay and enzyme-linked immunosorbent assay techniques.

Purification of cathepsin B by a new form of affinity chromatography

Human cathepsin B was purified by affinity chromatography on the semicarbazone of Gly-Phe-glycinal linked to Sepharose 4B, with elution by 2,2'-dipyridyl disulphide at pH 4.0. The product obtained in high yield by the single step from crude starting material was 80-100% active cathepsin B. The possibility that this new form of affinity chromatography may be of general usefulness in the purification of cysteine proteinases is discussed.