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Amino acid sequence of penicillopepsin. IV. Myxobacter AL-1 protease II and Staphylococcus aureus protease fragments and homology with pig pepsin and chymosin.

The digest of penicillopepsin (EC 3.4.23.7) with protease II from Myxobacter AL-1 gave five fragments which were separated on a Biogel P-100 column in 70% formic acid. The fragments were from 16 to 125 amino acids long. Two fragments were also isolated from a digest with a protease from Staphylococcus aureus. The analysis of these fragments by automatic sequencer gave a number of overlaps of the chymotryptic and thermolytic peptides. The available amino acid sequence data for penicillopepsin described in this paper and the accompanying papers (Kurosky, A. and Hofmann, T.:Can. J. Biochem. 54, 872 (1976);Rao, L and Hofmann, T.:Can. J. Biochem.54,885 (1976); Harris, C.I.,Rao, L., Shutsa, P., Kurosky, A. and Hofmann, T.: Can. J. Biochem. 54,895 (1976) have been combined and yield 15 fragments which range in lengths from 3 to 112 amino acid residues. These unique fragments account for virtually all the amino acids of the fungal protease. Four of the fragments with a total of 194 residues (about 60% of the molecule) have been aligned with corresponding sections of pig pepsin (EC 3.4.23.1) and with part of the N-terminal sequence available for calf chymosin (EC 3.4.23.4). In the alignments about 37% of the residues in the fungal enzyme are identical with at least one of the mammalian enzymes. An additional 20% are chemically similar. These results, together with previously reported active site directed modifications, show conclusively that penicillopepsin is an evolutionary homologue of the mammalian acid proteases.

Amino Acid Sequence↗

The growth hormone dependent serine protease inhibitor, Spi 2.1 inhibits the des (1-3) insulin-like growth factor-I generating protease.

The conversion of insulin-like growth factor-I (IGF-I) to the biologically more active des (1-3) IGF-I variant is catalyzed by a ubiquitous protease. This proteolytic activity is inhibited by human alpha1-antitrypsin and soy-bean trypsin inhibitor and is up-regulated in serum and tissue extracts of hypophysectomized rats. These observations lead us to investigate whether the growth hormone regulated, serine protease inhibitor, Spi 2.1 was able to inhibit the des (1-3) IGF-I generating protease. Dihydrofolate reductase deficient Chinese hamster ovary (CHO(dhfr-ve)) cells were transfected with a rat Spi 2.1 expression vector containing the dhfr and neomycin resistance gene. Stable transfectants were selected using G418 and amplified using methotrexate. Conditioned medium from Spi 2.1 transfected CHO cells potently inhibited proteolytic activity directed against a synthetic hexa-peptide with a sequence identical to the N-terminal of IGF-I. In contrast conditioned medium from wild-type CHO cells had little effect. Based upon these observations we suggest that our previous finding of enhanced des (1-3) IGF-I generating protease activity in growth hormone deficient rats may be, at least partly explained by reduced levels of Spi 2.1. Furthermore, we propose that the regulation of the generation of des (1-3) IGF-I may be an additional potential site of growth hormone regulation of IGF-I action.

Animals↗

Serine protease activity, bovine sperm protease, 66 kDa (BSp66), is present in hamster sperm and is involved in sperm-zona interaction.

Bovine sperm protease, 66 kDa (BSp66) is a serine protease previously characterized in bovine spermatozoa. Like other proteases, it may be present in sperm from other mammalian species different from bovine, playing a role in the fertilization process. In this study, we looked for BSp66 in hamster spermatozoa using heterologous antibodies against bovine BSp66. An immunoreactive protein was detected by Western blotting in mature and immature sperm. The detected protein had two isoforms similar to the ones reported in bovine sperm. Furthermore, indirect immune detection by fluorescence and electron microscopy assays, showed BSp66 signal at the acrosomal region similar to bovine sperm. As it was determined in bovine sperm, the acrosomal reaction displays the antigen within the acrosomal content. When live hamster sperm was incubated with polyclonal antibody against bovine BSp66 a decrease in the number of sperm bound to zona pellucida in homologous IVF and an impairment of head-head agglutination, were observed. These results suggest that a protease homologous to bovine BSp66 is present in golden hamster spermatozoa, with a conserved molecular mass and cellular location. Moreover, hamster BSp66 is probably involved in zona pellucida recognition.

Animals↗

Comparison of the reactions of neutral granulocyte proteases with the major plasma protease inhibitors and with antiplasmin.

Reaction mixtures of human serum and increasing amounts of granulocyte collagenase, elastase and chymotrypsin-like enzyme were studied by crossed immunoelectrophoresis utilizing antibodies against alpha1-antitrypsin, alpha1-antichymotrypsin, and antiplasmin. The increasing complex formation of alpha1-antitrypsin and alpha 1-antichymotrypsin with the different granulocyte proteases was not accompanied by any changes in the electrophoretic mobility or precipitate pattern of antiplasmin until the protease binding capacity of serum was saturated. The antiplasmin component in the reaction mixtures of human serum and granulocyte collagenase or elastase was not precipitated by antibodies against the proteases. The results indicate that none of the granulocyte proteases are bound by antiplasmin and that these enzymes do not activate plasminogen in serum.

Antibodies↗

TNF-alpha induces apoptosis mediated by AEBSF-sensitive serine protease(s) that may involve upstream caspase-3/CPP32 protease activation in a human gastric cancer cell line.

In the present study, we investigated the role of caspase-3/CPP32 and serine protease(s) in cell death induced by TNF-alpha in SNU-16 human gastric adenocarcinoma cells. Apoptosis induced in SNU-16 cells by TNF-alpha was accompanied by the activation of caspase-3/CPP32. After treatment with TNF-alpha, PKCdelta cleaved to its characteristic 40 kDa fragment in a caspase-3/CPP32 dependent manner. Incubation with z-DEVD-fmk completely abrogated TNF-alpha-induced DNA fragmentation, indicating that activation of caspase-3/CPP32 was crucially involved in TNF-alpha-induced apoptosis. In addition, serine protease inhibitor, 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF), clearly inhibited all the features of apoptosis including DNA fragmentation and chromatin condensation. Furthermore, in the AEBSF treated SNU-16 cells, only intact PKCdelta was detected by immunoblot analysis, suggesting that activation of caspase-3/CPP32 was blocked. Thus, the AEBSF-sensitive step may involve an upstream caspase-3/CPP32 protease activation. Taken together, these results suggest that both caspase-3/CPP32 and serine protease(s) are activated and play an important role in TNF-alpha induced apoptosis in SNU-16 cells.

Adenocarcinoma↗

Protease composition of exocytosed human skin mast cell protease-proteoglycan complexes. Tryptase resides in a complex distinct from chymase and carboxypeptidase.

We characterized the release and the protease composition of high m.w. complexes released from dispersed human skin mast cells, under conditions that did not disrupt the binding of proteases to proteoglycan. The net percent release ratio of tryptase to histamine, after anti-IgE and calcium ionophore A23187 stimulation was higher than those for chymase or carboxypeptidase. This was explained by the greater cell association of carboxypeptidase and chymase, compared with tryptase, after mast cell degranulation and/or differential cosedimentation of the proteases with mast cells, because treatment of activated mast cells with 1 M NaCl increased the release ratios of chymase and carboxypeptidase more than that of tryptase. Tryptase, after release, was stable in 0.12 M NaCl and had a molecular mass of approximately 200 to 250 kDa, suggesting that it was bound to proteoglycan. We demonstrated that complexes containing chymase and carboxypeptidase were separable from tryptase-containing complexes by gel filtration and by affinity chromatography. First, on fast protein liquid chromatography, released tryptase filtered at a molecular mass of approximately 200 to 250 kDa, compared with chymase and carboxypeptidase at 400 to 560 kDa. Second, by using affinity chromatography with immobilized antitryptase mAb in 0.15 M NaCl, carboxypeptidase and chymase activities were recovered primarily in the effluent and washes of an antitryptase antibody affinity column and cofiltered at 400 to 560 kDa. Tryptase was recovered only in the eluate. Finally, by using potato tuber carboxypeptidase inhibitor-Sepharose affinity chromatography, tryptase activity was found primarily in the effluent and washes, filtered at a molecular mass of 200 kDa on fast protein liquid chromatography, and was stable in 0.12 M NaCl buffer at 37 degrees C. Carboxypeptidase and chymase activities were found primarily in the eluate. These findings suggest that tryptase and carboxypeptidase/chymase reside in distinct macromolecular complexes. Separate complexes containing these proteases may help explain previous ultrastructural observations in which the distributions of chymase and tryptase within a single granule did not always coincide.

Carboxypeptidases↗

A novel serine protease (IRCM-serine protease 1) from porcine neurointermediate and anterior pituitary lobes. Isolation, polypeptide chain structure, inhibitor sensitivity, and substrate specificity with fluorogenic peptide substrates.

A novel serine protease, which we have called IRCM-serine protease 1, was purified from both porcine neurointermediate and anterior pituitary lobes. The enzyme was inhibited by soybean trypsin inhibitor, pancreatic trypsin inhibitor, benzamidine, phenylmethyl-sulfonyl fluoride, and thiol reagents including HgCl2, p-chloromercuribenzoate, and 5,5'-dithiobis-(2-nitrobenzoic acid) and was resistant to lima bean trypsin inhibitor, alpha 2-macroglobulin, alpha 1-antitrypsin, and C1-esterase inhibitor. IRCM-serine protease 1 displayed "trypsin-like" specificity toward a number of tripeptide coumarin-containing substrates, with kcat/km values ranging from 10(4) to 10(6) M-1 S-1. The best substrate was benzyloxycarbonyl-L-Ala-L-Lys-L-Arg-4-methylcoumarin-7-amide with a kcat/Km value of 2.27 X 10(6) M-1 S-1. IRCM-serine protease 1, Mr = 169,000-190,000 determined by gradient gel electrophoresis and gel filtration, respectively, appears to be a homologous dimer. The monomeric subunits of the enzyme are composed of an Mr = 38,000 polypeptide chain which is modifiable by 125I-D-Tyr-Glu-Phe-Lys-Arg-CH2Cl, disulfide-linked to another polypeptide resulting in a subunit molecular weight of 88,000.

Animals↗

[Changes of protein metabolism following irradiation. II. Protease activity, protease pattern, protein and free amino acids in the cytoplasm and cell organelles of the rat liver following 600 R whole-body irradiation].

The protease activity of cytoplasm and cell organelles of the rat liver against liver protein and hemoglobin as a substrate increases during an initial reaction phase on the first day after 600 R whole body X-irradiation. This is probably a consequence of the degradation of cellular debris. The protein, the protease activity and the free amino acids of the cytoplasm and the cell organelles decrease during the disease phase on day 3 and 4 after irradiation. The protein loss of the liver is therefore not explained by an increased protease activity. The protease activity and the free amino acids are increased in the cytoplasm and the cell organelles during the regeneration phase of the organism between day 15 and 18 after irradiation.

Amino Acids↗

Molecular cloning of effector cell protease receptor-1, a novel cell surface receptor for the protease factor Xa.

Cellular receptors for blood proteases regulate chemotaxis, extracellular proteolysis, and growth behavior of normal and malignant cells. Binding of the coagulation protease factor Xa to leukocytes is contributed by a recently identified molecule, denominated Effector cell Protease Receptor-1 (EPR-1). Monoclonal antibodies were generated against EPR-1+ MOLT13 lymphocytes and selected for reactivity with lymphocyte surface proteins by flow cytometry and with affinity-purified EPR-1 in Western blots. Antibody-based functional cloning of the cDNA for EPR-1 reveals the sequence of a novel molecule encoded by a prominent 1.9-kilobase mRNA. The cDNA predicts a glycoprotein of 337 amino acids, characterized by a unique cysteine-rich extracellular module, a single membrane-spanning domain, and a serine-rich (26%) cytoplasmic tail featuring at least 15 potential phosphorylation sites. Genetically engineered EPR-1 transfectants were recognized by monoclonal antibodies to EPR-1 and bound 125I-factor Xa in a specific and saturable manner (Kd approximately 10-15 nM). In the absence of factor V/Va, EPR-1 transfectants promoted prothrombin activation in a factor Xa concentration-dependent reaction, inhibited by a monoclonal antibody to EPR-1. These findings define EPR-1 as a novel cell surface receptor for factor Xa potentially implicated in protease-dependent cellular effector functions.

Amino Acid Sequence↗

Purification and characterization of an interleukin-1beta-converting enzyme family protease that activates cysteine protease P32 (CPP32).

CPP32, a member of the interleukin-1beta-converting enzyme (ICE) family of cysteine proteases, cleaves poly(ADP-ribose) polymerase and sterol regulatory element binding proteins during apoptosis. CPP32 normally exists in the cytosol as a 32-kDa inactive precursor and only becomes activated when cells are undergoing apoptosis. The activation is a proteolytic event that generates a p20/p11 heterodimer. We report here the identification, purification, and characterization of a hamster CPP32-activating protease (CAP) that cleaves and activates CPP32. The biochemical properties of CAP suggest that it is another member of the ICE family of proteases. Purified CAP consists of two prominent polypeptides of 19 and 13 kDa. Protein sequencing revealed that CAP is derived from the hamster homolog of Mch2alpha, a member of the ICE family recently identified based on the sequence conservation among the ICE family members. CAP activity is inhibited by CrmA, a cowpox virus protein that prevents host cell apoptosis. CAP itself is also activated through proteolytic cleavage. These data are consistent with the idea that the activation of the ICE family of proteases during apoptosis proceeds through a cascade of proteolytic events.

Amino Acid Sequence↗

Effects of fibroblasts and endothelial cells on inactivation of target proteases by protease nexin-1, heparin cofactor II, and C1-inhibitor.

Previous studies have shown that glycosaminoglycans in the extracellular matrix accelerate the inactivation of target proteases by certain protease inhibitors. It has been suggested that the ability of the matrix of certain cells to accelerate some inhibitors but not others might reflect the site of action of the inhibitors. Previous studies showed that fibroblasts accelerate the inactivation of thrombin by protease nexin-1, an inhibitor that appears to function at the surface of cells in extravascular tissues. The present experiments showed that endothelial cells also accelerate this reaction. The accelerative activity was accounted for by the extracellular matrix and was mostly due to heparan sulfate. Fibroblasts but not endothelial cells accelerated the inactivation of thrombin by heparin cofactor II, an abundant inhibitor in plasma. This is consistent with previous suggestions that heparin cofactor II inactivates thrombin when plasma is exposed to fibroblasts and smooth muscle cells. Neither fibroblasts nor endothelial cells accelerated the inactivation of C1s by plasma C1-inhibitor.

Amyloid beta-Protein Precursor↗

Impact of frequent natural polymorphisms at the protease gene on the in vitro susceptibility to protease inhibitors in HIV-1 non-B subtypes.

BACKGROUND: Naturally-occurring polymorphisms at the human immunodeficiency virus type 1 (HIV-1) protease which have been associated to resistance to protease inhibitors (PIs) in clade B viruses are frequently found in non-B subtypes, with unknown clinical significance. OBJECTIVE: To assess the susceptibility of non-B viruses to different PIs. STUDY DESIGN: Plasma samples from 58 drug-naive individuals infected with HIV-1 non-B subtypes (2A, 22C, 2D, 1F, 29G and 2J) defined by phylogenetic analyses of the protease gene were tested using a phenotypic assay (PhenoSense, ViroLogic, South San Francisco, CA, USA). Twenty of them were further analyzed with another assay (Antivirogram, Virco, Mechelen, Belgium). All 58 non-B viruses harbored amino acid substitutions associated with reduced PI susceptibility in clade B (positions 10, 20, 36, 63, 70, 77 and 82). RESULTS: Using PhenoSense-HIV assay, all but two individuals harbored viruses completely susceptible to all six PIs tested (indinavir (IDV), ritonavir (RTV), saquinavir (SQV), nelfinavir (NFV), amprenavir (APV), lopinavir (LPV)). The two viruses with reduced susceptibility belonged to clade G. The first virus, which had K20I, M36I and V82I, showed 2.9-fold decreased susceptibility to APV, while the second virus showed 3.9-fold decreased susceptibility to both NFV and RTV, with amino acid substitutions K20I, M36I, L63P and V82I. Of note, several other viruses displayed the same constellation of mutations but without showing any reduced susceptibility, suggesting that these polymorphisms per se do not affect PI susceptibility. CONCLUSION: PI susceptibility in HIV-1 non-B viruses seems to be preserved despite the presence of polymorphic changes which have been associated to PI resistance in clade B viruses.

Drug Resistance, Viral↗

Molecular basis of HIV-1 protease drug resistance: structural analysis of mutant proteases complexed with cyclic urea inhibitors.

In cell cultures, the key residues associated with HIV-1 resistance to cyclic urea-based HIV-1 protease (PR) inhibitors are Val82 and Ile84 of HIV-1 PR. To gain an understanding of how these two residues modulate inhibitor binding, we have measured the Ki values of three recombinant mutant proteases, I84V, V82F, and V82F/I84V, for DMP323 and DMP450, and determined the three-dimensional structures of their complexes to 2.1-1.9 A resolution with R factors of 18.7-19.6%. The Ki values of these mutants increased by 25-, 0.5-, and 1000-fold compared to the wild-type values of 0.8 and 0.4 nM for DMP323 and DMP450, respectively. The wild-type and mutant complexes overall are very similar (rms deviations of 0.2-0.3 A) except for differences in the patterns of their van der Waals (vdw) interactions, which appear to modulate the Ki values of the mutants. The loss of the CD1 atom of Ile84, in the I84V mutant complexes, creates a hole in the S1 subsite, reducing the number of vdw contacts and increasing the Ki values. The V82F mutant binds DMP323 more tightly than wild type because the side chain of Phe82 forms additional vdw and edge-to-face interactions with the P1 group of DMP323. The Ki values of the single mutants are not additive because the side chain of Phe82 rotates out of the S1 subsite in the double mutant (the chi 1 angles of Phe82 and -182 in the V82F and V82F/I84V mutants differ by 90 and 185 degrees, respectively), further reducing the vdw interactions. Finally, compensatory shifts in the I84V and V82F/ I84V complexes pick up a small number of new contacts, but too few to offset the initial loss of interactions caused by the mutations. Therefore, our data suggest that variants persist in the presence of DMP323 and DMP450 because of a decrease in vdw interactions between the mutant proteases and inhibitors.

Azepines↗

Cyclic urea amides: HIV-1 protease inhibitors with low nanomolar potency against both wild type and protease inhibitor resistant mutants of HIV.

Cyclic urea amides, a novel series of HIV-1 protease (HIV PR) inhibitors, have increased activity against drug-resistant mutants of the HIV PR. The design strategy for these inhibitors is based on the hypotheses that (i) the hydrogen-bonding interactions between the inhibitor and the protease backbone will remain constant for wild-type and mutant enzymes and (ii) inhibitors which are capable of forming many nonbonded interactions, distributed throughout the active site, will experience a lower percent change in binding energy as a result of mutation in the target enzyme than those that form fewer interactions by partial occupation of the active site. The cyclic urea amide, SD146, forms 14 hydrogen bonds and 191 van der Waals contacts to HIV PR. SD146 is a very potent antiviral agent (IC90 = 5.1 nM) against wild-type HIV and maintains the same or improved level of high potency against a range of mutant strains of HIV with resistance to a wide variety of HIV protease inhibitors.

Amides↗

Structural analysis of an HIV-1 protease I47A mutant resistant to the protease inhibitor lopinavir.

We have identified a rare HIV-1 protease (PR) mutation, I47A, associated with a high level of resistance to the protease inhibitor lopinavir (LPV) and with hypersusceptibility to the protease inhibitor saquinavir (SQV). The I47A mutation was found in 99 of 112,198 clinical specimens genotyped after LPV became available in late 2000, but in none of 24,426 clinical samples genotyped from 1998 to October 2000. Phenotypic data obtained for five I47A mutants showed unexpected resistance to LPV (86- to >110-fold) and hypersusceptibility to SQV (0.1- to 0.7-fold). Molecular modeling and energy calculations for these mutants using our structural phenotyping methodology showed an increase in the binding energy of LPV by 1.9-3.1 kcal/mol with respect to the wild type complex, corresponding to a 20- to >100-fold decrease in binding affinity, consistent with the observed high levels of LPV resistance. In the WT PR-LPV complex, the Ile 47 side chain is positioned close to the phenoxyacetyl moiety of LPV and its van der Waals interactions contribute significantly to the ligand binding. These interactions are lost for the smaller Ala 47 residue. Calculated binding energy changes for SQV ranged from -0.4 to -1.2 kcal/mol. In the mutant I47A PR-SQV complexes, the PR flaps are packed more tightly around SQV than in the WT complex, resulting in the formation of additional hydrogen bonds that increase binding affinity of SQV consistent with phenotypic hypersusceptibility. The emergence of mutations at PR residue 47 strongly correlates with increasing prescriptions of LPV (Spearman correlation r(s) = 0.96, P < .0001).

Drug Resistance, Viral↗

Construction of a human immunodeficiency virus type 1 (HIV-1) library containing random combinations of amino acid substitutions in the HIV-1 protease due to resistance by protease inhibitors.

Human immunodeficiency virus type 1 (HIV-1) heterogeneity contributes to the emergence of drug-resistant virus, escape from host defense systems, and/or conversion of the cellular tropism. To establish an in vitro system to address a heterogeneous virus population, we constructed a library of HIV-1 molecular clones containing a set of random combinations of zero to 11 amino acid substitutions associated with resistance to protease inhibitors by the HIV-1 protease. The complexity (2.1 x 10(5)) of the HIV-1 library pNG-PRL was large enough to cover all of the possible combinations of zero to 11 amino acid substitutions (a total of 4,096 substitutions possible). The T-cell line MT-2 was infected with the HIV-1 library, and resistant viruses were selected after treatment by the protease inhibitor ritonavir (0.03 to 0.30 microM). The viruses that contained three to eight amino acid substitutions could be selected within 2 weeks. These results demonstrate that this HIV-1 library could serve as an alternative in vitro system to analyze the emergence of drug resistance and to evaluate the antiviral activity of novel compounds against multidrug-resistant viruses.

Amino Acid Sequence↗

A targeted protease substrate for a quantitative determination of protease activities in the endolysosomal pathway.

Inside the cell, proteases act in concert in the degradation of proteins and peptides. In order to understand the significance of an individual proteolytic activity within an ensemble of proteases, protocols and probes are required that enable a quantitative determination of the contribution of a protease to the break-down of a given substrate. Here we present a fluorescence resonance energy transfer-based probe and protocols for a quantitative determination of proteolytic activities inside the endolysosomal compartment. A peptide substrate that is readily cleaved by different cathepsins is flanked by fluorescein and tetramethylrhodamine-labeled lysine residues. Efficient endolysosomal targeting of the substrate is achieved by N-terminal elongation with the cell-penetrating peptide nona-arginine. The proteasome inhibitor lactacystin has a small, but significant effect on the break-down of the substrate, thus demonstrating that only a minor fraction of the peptide reaches the cytoplasm in its intact form. Nona-arginine therefore constitutes a highly efficient low-molecular-weight moiety for targeting the endolysosomal compartment.

Catalysis↗

Protease inhibitors in rheumatoid synovial fluid. Analyses of electrophoretic homogeneity and protease inhibitory capacity.

Paired plasma and synovial fluids from 17 patients with seropositive rheumatoid arthritis were examined for electrophoretic homogeneity/heterogeneity and enzymic inhibitory capacity of the protease inhibitors. The high degree of saturation (approximately 90%) of the polyvalent protease inhibitor alpha 2-macroglobulin in the rheumatoid synovial fluid contrasts sharply with the low saturation of alpha 1-anti-trypsin. The inhibitory reactivity of the non-complexed fraction of both of these dominating antiproteases was retained (approximately 85-90%). Thus, a selective inactivation of synovial alpha 1-antitrypsin could not be demonstrated. alpha 1-Anti-chymotrypsin revealed electrophoretic homogeneity in all synovial fluids. Electrophoretic heterogeneity of the plasmin inhibitor antiplasmin was detected in the majority of synovial fluids indicating plasmin activation. The existence of a protease-antiprotease imbalance in the rheumatoid joint was indicated by the high degree of saturation of alpha 2-macroglobulin and a cleavage of C3 in rheumatoid synovial fluids.

Arthritis, Rheumatoid↗