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PubMed1978

Soluble pepstatins: a new approach to blockade in vivo of the renin-angiotensin system.

1. Synthesis of several pepstatin A derivatives was performed with the aim of increasing water solubility without altering the capacity to inhibit the renin-angiotensinogen reaction. 2. Pepstatinyl-arginine-O-methyl ester was studied in vitro and in vivo and compared with pepstatin A and with the arginine salt of pepstatin A. 3. This compound inhibited in vitro the reaction between purified hog renin and the synthetic renin N-acetyl-tetradecapeptide or the natural rat renin substrate. The inhibitory constant was of the same order of magnitude as that of pepstatin A. 4. In renal hypertensive rats, the bolus injection of pepstatinyl-arginine-O-methyl-ester or of the arginine salt of pepstatin decreased blood pressure to the same extent as a bolus injection of Sar1, Ala8-angiotensin II.

Animals↗
PubMed1996

Accelerated amyloid deposition in mice treated with the aspartic protease inhibitor, pepstatin.

The development of amyloidotic diseases is believed to be determined in large part by the structure and metabolism of the amyloid subunit protein. The amino-terminal region of serum amyloid A (SAA), the subunit precursor protein in reactive amyloidosis, appears to confer fibrillogenic potential. Here we present data consistent with the hypothesis that amyloid A fibrillogenesis is favored when proteolysis of the amino-terminal region of SAA is impaired. Murine tissue extracts were found to contain pepstatin-inhibitable protease activity that cleaved mouse SAA2 between Glu8 and Ala9. Tissues obtained from mice that had been treated with pepstatin for 3 days lacked this activity. To investigate a possible relationship between inhibition of aspartic proteases and amyloidogenesis, mice were treated with pepstatin while concurrently undergoing a standard amyloid induction protocol (repeated casein injections). Pepstatin-treated mice showed amyloid deposition significantly sooner than the control group, which had received only casein. During the preamyloidotic phase, pepstatin-treated mice had higher concentrations of SAA in serum and spleen than control mice. In addition, clearance of injected 125I-labeled SAA from plasma was significantly delayed. Based on these findings, it is reasonable to postulate that inhibition of aspartic protease activity can lead to an accumulation of amino-terminally intact SAA molecules and thereby accelerate amyloid fibril formation.

Animals↗
PubMed1995

Characterisation of a thermostable pepstatin-insensitive acid proteinase from a Bacillus sp.

An acid proteinase, Wai 21a, produced by a thermophilic Bacillus species (strain Wai 21a) has been purified to homogeneity by cation-exchange chromatography, phenyl-Sepharose chromatography and anion-exchange chromatography. A pI of 3.8 was determined by isoelectric focussing. The protein contained some associated carbohydrate (20 mol hexose equiv/mol proteinase). Optimal proteolytic activity was observed at pH 3.0 (at 60 degrees C). The Leu15-Tyr16 bond was the major site of hydrolysis for the oxidized B chain of insulin. Enzyme activity was not affected by inhibitors of the cysteine, metallo or serine class of proteinases. The aspartate proteinase inhibitor, pepstatin, did not inhibit enzyme activity. Inhibition of enzyme activity by 1,2-epoxy-3-(p-nitrophenoxy)-propane indicated the presence of at least one carboxyl group essential to the catalytic mechanism of the enzyme. Proteinase activity was inhibited by diazoacetyl-DL-norleucine methyl ester in a slow and non-specific manner atypical of pepstatin-sensitive aspartate proteinases. Wai 21a proteinase may be classified as member of the pepstatin-insensitive group of aspartate proteinases. The thermal stability at pH 3.0 and 60 degrees C increased 2.1-fold (t1/2, 4.5-9.7 hr) in the presence of 5 mM Ca++. An increase in both pH (3.0-4.5) and Ca++ concentration (0-30 mM) resulted in a 15-fold increase (t1/2, 15-230 min) in thermal stability at 75 degrees C. The amino acid composition of Wai 21a proteinase was found to be similar to other pepstatin-insensitive proteinases from bacterial sources and in particular similar to the other pepstatin-insensitive proteinases from bacterial sources and in particular similar to the thermostable enzyme, kumamolysin.

Amino Acid Sequence↗
PubMed2006

Replacement of isobutyl by trifluoromethyl in pepstatin A selectively affects inhibition of aspartic proteinases.

Two bis-trifluoromethyl pepstatin A analogues, carboxylic acid 1 and its methyl ester 2, have been synthesised in order to probe the properties and size of the trifluoromethyl (Tfm) group and compare it to the "bigger" isobutyl that is present in pepstatin A. The results demonstrate that Tfm can effectively replace the isobutyl chain as far as inhibitory activity against plasmepsin II (PM II), an aspartic proteinase from Plasmodium falciparum, is concerned. On the other hand, replacement of isobutyl by Tfm selectively affected activity against other aspartic proteinases tested. Two lines of evidence led to these conclusions. Firstly, compounds 1 and 2 retained single-digit nanomolar inhibitory activity against PM II, but were markedly less active against PM IV, cathepsin D and cathepsin E. Secondly, the X-ray crystal structures of the three complexes of PM II with 1, 2 and pepstatin A were obtained at 2.8, 2.4 and 1.7 A resolution, respectively. High overall similarity among the three complexes indicated that the central Tfm was well accommodated in the lipophilic S1 pocket of PM II, where it was involved in tight hydrophobic contacts. The interaction of PM II with Phe111 appeared to be crucial. Comparison of the crystal structures presented here, with X-ray structures or structural models of PM IV and cathepsin D, allowed an interpretation of the inhibition profiles of pepstatin A and its Tfm variants against these three enzymes. Interactions of the P1 side chain with amino acids that point into the S1 pocket appear to be critical for inhibitory activity. In summary, Tfm can be used to replace an isobutyl group and can affect the selectivity profile of a compound. These findings have implications for the design of novel bioactive molecules and synthetic mimics of natural compounds.

Animals↗
PubMed1995

Crystal structure of human pepsin and its complex with pepstatin.

The three-dimensional crystal structure of human pepsin and that of its complex with pepstatin have been solved by X-ray crystallographic methods. The native pepsin structure has been refined with data collected to 2.2 A resolution to an R-factor of 19.7%. The pepsin:pepstatin structure has been refined with data to 2.0 A resolution to an R-factor of 18.5%. The hydrogen bonding interactions and the conformation adopted by pepstatin are very similar to those found in complexes of pepstatin with other aspartic proteinases. The enzyme undergoes a conformational change upon inhibitor binding to enclose the inhibitor more tightly. The analysis of the binding sites indicates that they form an extended tube without distinct binding pockets. By comparing the residues on the binding surface with those of the other human aspartic proteinases, it has been possible to rationalize some of the experimental data concerning the different specificities. At the S1 site, valine at position 120 in renin instead of isoleucine, as in the other enzymes, allows for binding of larger hydrophobic residues. The possibility of multiple conformations for the P2 residue makes the analysis of the S2 site difficult. However, it is possible to see that the specific interactions that renin makes with histidine at P2 would not be possible in the case of the other enzymes. At the S3 site, the smaller volume that is accessible in pepsin compared to the other enzymes is consistent with its preference for smaller residues at the P3 position.

Amino Acid Sequence↗
PubMed2006

Chymostatin can combine with pepstatin to eliminate extracellular protease activity in cultures of Aspergillus niger NRRL-3.

Aspergillus strains are being considered as potential hosts for recombinant heterologous protein production because of their excellent extracellular enzyme production characteristics. However, Aspergillus proteases are problematic in that they modify and degrade the heterologous proteins in the extracellular medium. In previous studies we observed that media adjustments and maintenance of a filamentous morphology greatly reduced protease activity and that a low concentration of the aspartic protease inhibitor pepstatin inhibited the latter protease activity to the extent of approximately 90%. In this paper we report that when the serine protease inhibitor chymostatin is used in combination with pepstatin 99-100% of total protease activity in Aspergillus cultures is inhibited. In protease assays a concentration of 30 microM chymostatin combined with 0.075 microM pepstatin was required for maximum inhibition. Inhibitor concentrations of chymostatin and pepstatin of 120 and 0.3 microM, respectively, when added to Aspergillus cultures, has no significant effect on biomass production, glucose utilization or culture pH pattern. The potential of using these protease inhibitors in cultures of recombinant Aspergillus strains producing heterologous proteins will now be investigated to determine if the previously observed recombinant protein denaturing effects of Aspergillus proteases can be negated.

Aspartic Acid Endopeptidases↗
PubMed1991

Accumulation of pepstatin in cultured endothelial cells and its effect on endothelial processing.

Aspartic acid proteases have been implicated in the processing of ET-1(1-39) to ET-1(1-21). To further understand the role of this class of enzymes in ET-1 synthesis, cultured vascular endothelial cells were incubated with pepstatin, and the accumulation of the inhibitor and its effect on the processing of ET-1(1-39) was examined. Pepstatin accumulated in the cells in a time-dependent manner, to a concentration (greater than 10(-7) M) sufficient to inhibit aspartic acid proteases. Pepstatin did not alter the ratio of ET-1(1-21) to ET-1(1-39), nor did it affect the rate of secretion of either peptide. When endothelial cells were incubated with phosphoramidon under identical conditions, the secretion of ET-1(1-21) was significantly reduced with a concomitant increase in the secretion of ET-1(1-39). These results suggest that the processing of ET-1(1-39) does not involve a pepstatin-sensitive aspartic acid protease, and that the enzyme responsible for generating ET-1(1-21) is sensitive to phosphoramidon.

Amino Acid Sequence↗
PubMed1986

Schistosoma japonicum: ultrastructural localization of a hemoglobinase using mercury labeled pepstatin.

Mercury labeled pepstatin was used to demonstrate the site of a pepstatin sensitive hemoglobinase in paraformaldehyde fixed adult Schistosoma japonicum. Pepstatin was covalently attached to glutathione using dicyclohexylcarbodiimide followed by addition to methyl mercury chloride. Deposition of mercury was observed in lipid-like globules and autophagic vacuoles in the gastrodermis. Control studies were negative in all instances. These results complement previous cytochemical studies on the distribution of other acid hydrolases in the gastrodermis of schistosomes. It is hypothesized that this pepstatin sensitive enzyme probably belongs to the carboxyl class of proteinases.

Animals↗
PubMed1991

Purification of HIV-1 wild-type protease and characterization of proteolytically inactive HIV-1 protease mutants by pepstatin A affinity chromatography.

Recombinant wild-type protease of human immunodeficiency virus, type 1 (HIV-1) expressed in E. coli was purified by pepstatin A affinity chromatography. An 88-fold purification was achieved giving a protease preparation with a specific enzymatic activity of approximately 3700 pmol/min/micrograms. Two proteolytically inactive HIV-1 mutant proteases (Arg-87----Lys; Asn-88----Glu) were found to bind to pepstatin A agarose, and and they were purified as the wild-type protease. A third mutant protease Arg-87----Glu) was apparently unable to bind to pepstatin A under similar conditions. Binding to pepstatin A indicates the binding ability of the substrate binding site and the ability to form dimers. These features may be used to purify and to characterize other mutated HIV-1 proteases.

Amino Acid Sequence↗
PubMedDate not supplied

Polymerizing properties of pepstatin A.

Pepstatin A, a pentapeptide aspartyl protease inhibitor, can spontaneously polymerize into filaments having a helical substructure and, after negative staining, characteristic diameters ranging from 6 to 12 nm. Optical diffraction analysis demonstrated that these filaments consist of a 6-nm-wide strand helically wound with a periodic pitch of 25 nm. Selected images suggest that these filaments may actually be composed of two, intertwined 6-nm-wide strands, an hypothesis not at variance with the diffraction data. These filaments may extend over several micrometers. At low ionic strength and neutral pH, the critical concentration for pepstatin A filament assembly is 0.1 mM. At higher pepstatin A concentrations or in physiological salt solutions, a variety of higher order structures were observed, including ribbons, sheets, and cylinders with both regular and twisted or irregular geometries. Pepstatin A polymerized into these higher order structures loses its ability to inhibit the aspartyl protease of the human immunodeficiency virus type 1. These results have implications not only for model studies on the polymerization of small peptides into higher order structures, but also for the practical development of soluble protease inhibitors.

Microscopy, Electron↗
PubMed2005

Self-assembled monolayer of a pepstatin fragment as a sensing element for aspartyl proteases.

A novel disulfide, which carried two pepstatin fragments at both ends, was prepared by the coupling of 11,11'-dithiobisundecanoic acid (DTUA) with a fragment (Val-Val-Sta) carrying a n-hexyl end (Pepsta(h)). The compound obtained (DTUA-Pepsta(h)) formed a self-assembled monolayer (SAM) on a gold electrode and vacuum-evaporated gold thin film as proven by cyclic voltammetry and reflection absorption infrared spectroscopy, respectively. When the SAM-modified gold electrode was incubated with a solution of aspartyl protease, pepsin, a decrease in both anodic and cathodic peak currents and an increase in potential difference were observed in the cyclic voltamogram of hydroquinone as a probe, whereas a coexistence of free pepstatin fragment inhibited these phenomena, indicating the specific binding of pepsin to the fragment at the exterior of the SAM. The binding rate of the enzyme to the SAM was largely dependent on the surface density of the fragment moiety in the SAM. Furthermore, when the SAM of DTUA-Pepsta(h) on a gold colloid array deposited on an amino group-modified glass plate was immersed in a pepsin solution, absorption of the glass plate at 550 nm corresponding to a localized surface plasmon resonance of the gold colloid abruptly increased and slightly red-shifted, and a further addition of pepstatin A gradually decreased the absorbance. From the increasing and decreasing profiles of absorbance, the association constant (K(assoc)) for pepsin with the fragment on the SAM was determined. Similar phenomena were observed upon immersion of the fragment-modified SAM in a solution of HIV-1 protease, suggesting a usability of the pepstatin fragment SAM for the detection and removal of the enzyme from biological fluids.

Aspartic Acid Endopeptidases↗
PubMed1982

The effects of lactoyl-pepstatin and the pepsin inhibitor peptide on pig cathepsin D.

Lactoyl-pepstatin (an acylated tetrapeptide) is much more readily soluble in aqueous media than the more common isovaleryl- and acetyl-pepstatins (acylated pentapeptides). However, the K1 value for inhibition of cathepsin D by lactoyl-pepstatin at pH 3.5 is approx. 10(-7) M, some two to three orders of magnitude weaker than has been obtained previously for isovaleryl- or acetyl-pepstatins. One of the peptides released during activation of pig pepsinogen is known to be an effective inhibitor of pig pepsin, but it does not alter the activity of the similar aspartic proteinase, pig cathepsin D.

Animals↗
PubMed1993

X-ray-crystallographic studies of complexes of pepstatin A and a statine-containing human renin inhibitor with endothiapepsin.

H-189, a synthetic human renin inhibitor, and pepstatin A, a naturally occurring inhibitor of aspartic proteinases, have been co-crystallized with the fungal aspartic proteinase endothiapepsin (EC 3.4.23.6). H-189 [Pro-His-Pro-Phe-His-Sta-(statyl)-Val-Ile-His-Lys] is an analogue of human angiotensinogen. Pepstatin A [Iva(isovaleryl)-Val-Val-Sta-Ala-Sta] is a blocked pentapeptide which inhibits many aspartic proteinases. The structures of the complexes have been determined by X-ray diffraction and refined to crystallographic R-factors of 0.15 and 0.16 at resolutions of 0.18 nm (1.8 A) and 0.2 nm (2.0 A) respectively. H-189 is in an extended conformation, in which the statine residue is a dipeptide analogue of P1 and P'1 as indicated by the conformation and network of contacts and hydrogen bonds. Pepstatin A has an extended conformation to the P'2 alanine residue, but the leucyl side chain of the terminal statine residue binds back into the S'1 subsite, and an inverse gamma-turn occurs between P'1 and P'3. The hydroxy moiety of the statine at P1 in both complexes displaces the solvent molecule that hydrogen-bonds with the catalytic aspartate residues (32 and 215) in the native enzyme. Solvent molecules originally present in the native structure at the active site are displaced on inhibitor binding (12 when pepstatin A binds; 16 when H-189 binds).

Amino Acid Sequence↗
PubMed1999

Subsite preferences of pepstatin-insensitive carboxyl proteinases from bacteria.

Pseudomonas sp. 101 carboxyl proteinase (PCP) and Xanthomonas sp. T-22 carboxyl proteinase (XCP), the first and second unique carboxyl proteinases from prokaryotes to be isolated and characterized, are not inhibited by the classical carboxyl proteinase inhibitor pepstatin. In this study, we elucidated their subsite preferences by using a series of synthetic chromogenic substrates, Lys-Pro-Ile(P3)-Glu(P2)-Phe*Nph-Arg(P2')-Leu(P3') (Nph is p-nitrophenylalanine, Phe*Nph is the cleavage site) with systematic substitutions at the P3, P2, P2', and P3' positions. Among 45 substrates tested, the best substrate for PCP had a Leu replacement at the P2 position (kcat = 27.2 s-1, Km = 4.22 microM, kcat/Km = 6.43 microM-1.s-1), and that for XCP had an Ala replacement at the P3 position (kcat = 79.4 s-1, Km = 6.05 microM, kcat/Km = 13.1 microM-1. s-1). PCP and XCP preferred such charged amino acid residues as Glu, Asp, Arg, or Lys at the P2' position. This suggested that the S2' subsites of PCP and XCP are occupied by hydrophilic residues, similar to that of pepstatin-insensitive carboxyl proteinase from Bacillus coagulans J-4 [Shibata et al. (1998) J. Biochem. 124, 642-647]. In contrast, the S2' subsite of pepstatin-sensitive carboxyl proteinases (aspartic proteinases) is hydrophobic in nature. Thus, the hydophilic nature of the S2' subsite appears to be a distinguishing feature of pepstatin-insensitive carboxyl proteinases.

Aspartic Acid Endopeptidases↗
PubMed1976

The structure and function of acid proteases. V. Comparative studies on the specific inhibition of acid proteases by diazoacetyl-DL-norleucine methyl ester, 1,2-epoxy-3-(p-nitrophenoxy) propane and pepstatin.

Comparative studies have been made on the effects of diazoacetyl-DL-norleucine methyl ester (DAN), 1,2-epoxy-3-(p-nitrophenoxy)propane (EPNP) and pepstatin on acid proteases, including those from Acrocylindrium sp., Aspergillus niger, Aspergillus saitoi, Mucor pusillus, Paecilomyces varioti, Rhizopus chinensis, and Trametes sanguinea, and also porcine pepsin [EC 3.4.23.1] and calf rennin [EC 3.4.23.4] for comparative purposes. These enzymes were rapidly inactivated at similar rates and in 1:1 stiochiometry by reaction with DAN in the presence of cupric ions. The pH profiles of inactivation of these enzymes were similar and had optima at pH 5.5 to 6. They were also inactivated at similar rates by reaction with EPNP, with concomitant incorporation of nearly 2 EPNP molecules per molecule of enzyme. The pH profiles of inactivation were again similar and maximal inactivation was observed at around pH 3 to 4. Some of the EPNP-inactivated enzymes were treated with DAN and shown still to retain reactivity toward DAN. All these enzymes were inhibited strongly by pepstatin, and the reactions of DAN and EPNP with them were also markedly inhibited by prior treatment with pepstatin. These results indicate that the active sites of these enzymes are quite similar and that they presumably have at least two essential carboxyl groups at the active site in common, one reactive with DAN in the presence of cupric ions and the other reactive with EPNP, as has already been demonstrated for porcine pepsin and calf rennin. Pepstatin appears to bind at least part of the active site of each enzyme in a simmilar manner.

Aminocaproates↗
PubMed1978

Treatment of mouse muscular dystrophy with the protease inhibitor pepstatin.

Dystrophic mice were treated for 5 weeks beginning at 3 weeks of age with 20 ugm per day of pepstatin, a potent inhibitor of cathepsin D. Mortality was less and weight gain greater in pepstatin treated mice than in controls. Muscle bulk was greater and hind lamb contractures were reduced in treated mice. Mean muscle fiber mass was significantly increased by pepstatin treatment. Inhibition of muscle protease may be the mechanism by which pepstatin slows the tempo of progression of mouse muscular dystrophy.

Animals↗
PubMed1999

Structure of the Rhizomucor miehei aspartic proteinase complexed with the inhibitor pepstatin A at 2.7 A resolution.

Crystals of Rhizomucor miehei aspartic proteinase (RMP) complexed with pepstatin A grew in the orthorhombic space group P212121 and were isomorphous to native RMP crystals. The unit-cell dimensions are a = 41.52, b = 50.82, c = 172.71 A. There is one RMP-pepstatin A complex per asymmetric unit. The structure of the RMP-pepstatin A complex has been refined to a crystallographic R value of 19.3% and an Rfree value of 28.0% at 2.7 A resolution. A pepstatin A molecule fits into the large substrate-binding cleft between the two domains of RMP in an extended conformation up to the alanine residue at the P2' position. The dipeptide analogue statine residue at the P3'-P4' position forms an inverse gamma-turn (P3'-P1') with the statine residue at the P1-P1' position and its leucyl side chain binds back into the S1' subsite. The inhibitor interacts with the residues of the substrate-binding pocket by both hydrogen bonds and hydrophobic interactions. The hydroxyl group of the statine residue at the P1-P1' position forms hydrogen bonds with both catalytic aspartate residues (Asp38 and Asp237). This conformation mimics the expected transition state of the enzyme-substrate interaction. The binding of the inhibitor to the enzyme does not produce large distortions of the active site. No domain movement was observed compared with the native enzyme structure. However, the surface-flap region (residues 82-88) undergoes a conformational change, moving toward the inhibitor and becoming rigid owing to the formation of hydrogen bonds with the inhibitor. B-factor calculations of the two domains suggest that the C-terminal domain becomes more rigid in the complex than in the native structure.

Aspartic Acid Endopeptidases↗
PubMedDate not supplied

Plasmodium falciparum: differential sensitivity in vitro to E-64 (cysteine protease inhibitor) and Pepstatin A (aspartyl protease inhibitor).

We investigated the effect of a cysteine proteinase inhibitor (E-64) and an aspartyl proteinase inhibitor (Pepstatin A) on asexual erythrocytic stages of Plasmodium falciparum in culture. These two protease inhibitors showed different patterns of activity. E-64 acted preferentially against trophozoite and schizont stages. After 48 h incubation at high concentrations of E-64 (28, 140, 280 microM), growth was totally abolished and the parasites presented characteristic enlarged food vacuoles. Morphological alterations were also seen after shorter incubation periods (6 h at 28 microM) or 12 h at the inhibitory concentration 50% (12 microM), but an additional culture period (24 h) in inhibitor-free medium allowed normal parasite development, demonstrating a parasitostatic effect. E-64 acts on parasite multiplication; the normal merozoite maturation was altered and the normal reinvasion process partially impaired. Pepstatin A used at the inhibitory concentration 50% (4 microM) killed the parasites before trophozoite development and had a major effect on schizonts maturation. No altered parasite development occurred during an additional culture period without Pepstatin A, demonstrating a parasiticidal effect. E-64 and Pepstatin A used in combination inhibit the parasite growth with a strong synergistic effect.

Animals↗