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PubMed1998

Protease in normal human epidermal keratinocytes.

An in vitro normal human epidermal keratinocytes (NHEK) model was used to study and to characterize the protease stimulated by the mustards 2-chloroethyl ethyl sulphide (CEES), 2-chloro-N-(2-chloroethyl)-N-methylethanamine hydrochloride (nitrogen mustard, HN2), and Bis-2-chloroethyl sulfide (sulfur mustard, HD). The results obtained by using a chromozym (TRY) peptide substrate protease assay showed the optimum mustard concentration and time for protease stimulation to be about 200 microM CEES, 100 microM HN2 or HD, and 16 hours. The mustard-stimulated protease was membrane-bound, and was inhibited by adding a Ca2+ chelator EGTA (2 mM), BAPTA AM (50 microM) or a serine protease inhibitor diisopropyl fluoro-phosphate DFP (1 mM), or a protein synthesis inhibitor cycloheximide (10 microM) in the extracellular medium. These results suggest that one of the mechanisms of mustard toxicity is via the stimulation of a trypsin/chymotrypsin like serine protease, which is dependent on Ca2+ and new protein synthesis. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed a mustard-stimulated approximately equal to 70-80 KDa protein band that was associated with protease activity which was inhibitable by EGTA, BAPTA, DFP or cycloheximide. This mustard-stimulated protein (protease) may serve as a diagnostic tool for mustard exposure as well as an assay for screening prospective antivesicant protease inhibitor drugs.

Cells, Cultured↗
PubMed2005

Fibrillar amyloid beta-protein inhibits the activity of high molecular weight brain protease and trypsin.

The effect of soluble amyloid beta-protein (sAbeta) and fibrillar amyloid beta-protein (fAbeta) on the casein-digesting activity of high molecular weight bovine brain protease (HMW protease) and trypsin was studied. While sAbeta stimulated the casein-digesting activity of HMW protease in a concentration-dependent manner, it did not affect trypsin activity. Structure-activity relationship was studied by testing different soluble and fibrillar Abeta peptides. Various Abeta peptides affected casein-digesting activity of HMW protease differently: sAbeta 1-40 > sAbeta 22-35 = sAbeta 1-11 = sAbeta1-16 > sAbeta 1-28 = sAbeta 31-35, while sAbeta 12-28 and sAbeta 25-35 had no effect. On the other hand, among the fibrillar beta peptides, only fAbeta 1-40 significantly inhibited the casein-digesting activity of HMW protease. Tricine gel electrophoresis showed that sAbeta was digested by trypsin while it remained un-cleaved in the presence of HMW protease. However, fAbeta, a major component of amyloid plaques in Alzheimer's disease, inhibited the casein-digesting activity of both HMW protease and trypsin. fAbetawas found to be resistant to proteolysis by HMW protease and trypsin. The trypsin resistance starts in the early stage of fibrillization of Abeta, i.e., aggregated Abeta. Taken together, these results suggest that fibrillization of Abeta may affect the clearance of Abeta by inhibiting the brain proteases, thereby increasing the concentration of circulating Abeta, that may further increase the Abeta fibrillization.

Alzheimer Disease↗
PubMed2001

Effect of inhibitors of cysteine and serine proteases in anticancer drug-induced apoptosis in gastric cancer cells.

Activation of proteases can play an important role in apoptotic cell death induced by anticancer drugs. To assess involvement of activation of cysteine and serine proteases in anticancer drug-induced apoptosis, we tested effect of inhibitors of cysteine and serine proteases on sensitivity to anticancer drugs in MKN45 gastric cancer cells. Cytotoxic effect by adriamycin (ADM), SN-38 (active form of irrinotecan) and cisplatin (CDDP) was significantly prevented by cotreatment with Z-Val-Ala-Asp-fluoromethylketone (Z-VAD-fmk) (p<0.01), a pancaspase inhibitor compared with drug alone using MTT assay. In contrast, cotreatment with N-acetyl-Tyr-Val-Ala-Asp aldehyde (AC-YVAD-CHO), a caspase 1 inhibitor did not prevent any cytotoxic effect of these drugs. Cotreatment of N-acetyl-Asp-Glu-Val-Asp aldehyde (AC-DEVD-CHO), a caspase 3 inhibitor prevented cytotoxic effect of VP-16 and SN-38 (p<0.01). Prevention of these cytotoxic effects by caspase inhibitors was not dose-dependent. Cotreatment of N-tosyl-L-lysyl chloromethylketone (TLCK), a serine protease inhibitor significantly prevented cytotoxic effect of ADM, SN-38, 5-fluorouracil (5-FU) and CDDP in a slight dose-dependent manner (p<0.01) except for etoposide (VP-16) and docetaxel (TXT), while an other serine protease inhibitor, N-tosyl-L-phenylalanyl chloromethylketone (TPCK) did not prevent any anticancer drug-induced cytotoxic effect. These effects were associated with prevention of internucleosomal DNA ladder formation in apoptosis. Further, protease inhibitors did not block induction of cytochrome c, that can explain the partial effect of prevention by anticancer-induced cell death. These results suggest that anticancer drug-induced cytotoxic effect is mediated by activation of serine protease (caspase-independent) as well as caspase-dependent pathway leading to apoptotic cell death, and that protease-independent pathway may also be involved in apoptotic pathways. The involvement of protease in signal transduction pathways may differ in cytotoxic action of drugs in gastric cancer cells.

Antineoplastic Agents↗
PubMed2006

Sites in the CH3 domain of human IgA1 that influence sensitivity to bacterial IgA1 proteases.

The influence of regions, other than the hinge, on the susceptibility of human IgA1 to cleavage by diverse bacterial IgA1 proteases, was examined using IgA1 mutants bearing amino acid deletions, substitutions, and domain swaps. IgA1 lacking the tailpiece retained its susceptibility to cleavage by all of the IgA1 proteases. The domain swap molecule alpha1alpha2gamma3, in which the CH3 domain of IgA1 was exchanged for that of human IgG1, was resistant to cleavage with the type 1 and 2 serine IgA1 proteases of Neisseria meningitidis, Neisseria gonorrhoeae, and Haemophilus influenzae, but remained sensitive to cleavage with the metallo-IgA1 proteases of Streptococcus pneumoniae, Streptococcus oralis, Streptococcus sanguis, and Streptococcus mitis. Substitution of the IgA1 Calpha3 domain motif Pro440 -Phe443 into the corresponding position in the Cgamma3 domain of alpha1alpha2gamma3 resulted now in sensitivity to the type 2 IgA1 protease of N. meningitidis, indicating the possible requirement of these amino acids for sensitivity to this protease. For the H. influenzae type 2 protease, resistance of an IgA1 mutant in which the CH3 domain residues 399-409 were exchanged with those from IgG1, but sensitivity of mutant HuBovalpha3 in which the Calpha3 domain of bovine IgA replaces that of human IgA1, suggests that CH3 domain residues Glu403, Gln406, and Thr409 influence sensitivity to this enzyme. Hence, unlike the situation with the metallo-IgA1 proteases of Streptococcus spp., the sensitivity of human IgA1 to cleavage with the serine IgA1 proteases of Neisseria and Haemophilus involves their binding to different sites specifically in the CH3 domain.

Amino Acid Sequence↗
PubMed1999

A protease isolated from human plasma activating factor VII independent of tissue factor.

An activity detected in a prothrombin complex concentrate, termed 'thrombin-like' due to its amidolytic properties, was recently reported by another working group. This serine-protease revealed partial structural homology with a 'hepatocyte growth factor activator'. An impact of this protease on coagulation has not yet been described. The protease was isolated from plasma fractions by ion exchange chromatography and adsorption to immobilized heparin and/or aprotinin. Clotting tests including the FVIIa-rTF assay were performed employing coagulometry. A monoclonal antibody-derived F(ab')2 to FVIII was used to investigate the FVIII bypassing activity (FEIBA). The identity of the-protease with the so-called 'thrombin-like' protease was supported by sequencing of the amino-termini. Its amidolytic activity was significantly enhanced in the presence of calcium and/or heparin. Incubation with purified FVII revealed the generation of FVIIa, but was prevented by pre-incubation of the protease with aprotinin. In contrast, purified FV and FVIII were inactivated. Studying coagulation parameters, clotting times like plasma recalcification times and the prothrombin times were found to be shortened by addition of the protease. Employing a FVIII-inhibitory F(ab')2 and enhancing clotting times significantly, FEIBA of the protease was found. We demonstrated that the isolated protease activates FVII independent of tissue factor. Net acceleration of coagulation was found in several global clotting assays resulting in an in vitro FEIBA. The physiological relevance of these findings deserves further investigation.

Amidohydrolases↗
PubMed2002

Activation of chymotrypsin-like serine protease(s) during apoptosis detected by affinity-labeling of the enzymatic center with fluoresceinated inhibitor.

There is evidence in the literature that serine (Ser) proteases, like caspases, are activated during apoptosis. Little is known, however, about individual Ser proteases and the mechanism of their activation. In the present study, we employed a new type of cell permeant reagent to detect activation of chymotrypsin-like proteases in human leukemic HL-60 cells induced to undergo apoptosis. The reagent, 5(6)-carboxyfluoresceinyl-L-phenylalanyl-chloromethyl ketone (FFCK), is a fluorochrome-labeled analog of N-tosyl-L-phenylalanine chloromethyl ketone (TPCK), the inhibitor known to specifically and covalently bind to the active center of chymotrypsin-like enzymes. In cultures treated with the DNA topoisomerase I inhibitor, camptothecin (CPT), or tumor necrosis factor (TNFalpha), populations of cells appeared that had the capability to bind FFCK. Most FFCK-binding cells were identified by fluorescence microscopy and laser scanning cytometry (LSC) as the cells undergoing apoptosis. Frequency of cells binding FFCK strongly correlated with frequency of cells having activated caspases (r=0.98 in CPT-treated, and r=0.99 in TNFalpha-treated cultures). The observed induction of FFCK binding we interpret as representing the activation of a chymotrypsin-like apoptotic Ser protease(s). Pretreatment of cells with the poly-caspase inhibitor, Z-VAD-FMK, prevented the activation of these Ser protease(s). Pretreatment with TPCK, however, had a less pronounced, although distinct and reproducible suppressive effect, on caspase activation. The data, thus, suggest that activation of caspases is an upstream event required for activation of Ser protease(s). Activation of the latter, however, appears to additionally amplify, in a cascade-like mode, caspases activation. Differential color fluorochrome-labeling allowed us to discriminate, within the same cells, between the activation of active caspases and Ser protease(s). Despite a certain degree of co-localization, the inter- and intra-cellular pattern of caspase- vs. Ser-protease(s) was different. Our approach makes it possible to simultaneously monitor activation of caspases and Ser proteases in the same live cells that are induced to apoptosis.

Affinity Labels↗
PubMedDate not supplied

Sequential activation of caspases and serine proteases (serpases) during apoptosis.

Analogous to caspases, serine (Ser) proteases are involved in protein degradation during apoptosis. It is unknown, however, whether Ser proteases are activated concurrently, sequentially, or as an alternative to the activation of caspases. Using fluorescent inhibitors of caspases (FLICA) and Ser proteases (FLISP), novel methods to detect activation of these enzymes in apoptotic cells, we demonstrate that two types of Ser protease sites become accessible to these inhibitors during apoptosis of HL-60 cells. The prior exposure to caspases inhibitor Z-VAD-FMK markedly diminished activation of both Ser protease sites. However, the unlabeled inhibitor of Ser-proteases TPCK had modest suppressive effect- while TICK had no effect- on the activation of caspases. Activation of caspases, thus, appears to be an upstream event and likely a prerequisite for activation of FLISP-reactive sites. Differential labeling with the red fluorescing sulforhodamine-tagged VAD-FMK and the green fluorescing FLISP allowed us to discriminate, within the same cell, between activation of caspases and Ser protease sites. Despite a certain degree of co-localization, the pattern of intracellular caspase- vs FLISP- reactive sites, was different. Also different were relative proportions of activated caspases vs Ser protease sites in individual cells. The observed induction of FLISP-binding sites we interpret as revealing activation of at least two different apoptotic Ser proteases; by analogy to caspases we denote them serpases. Their apparent molecular weight (62-65 kD) suggests that they are novel enzymes.

Amino Acid Chloromethyl Ketones↗
PubMed1992

Purification and characterization of the mouse mammary tumor virus protease expressed in Escherichia coli.

The mouse mammary tumor virus (MMTV) protease gene was cloned into pGEX-2T, an Escherichia coli expression vector containing the glutathione S-transferase coding region of Schistosoma japonicum. The chimeric protein was formed by fusion of the glutathione S-transferase with a hexapeptide which contains a thrombin cleavage site, followed by the MMTV protease. Affinity chromatography on a glutathione-Sepharose 4B column was used to isolate the chimeric protein. After thrombin cleavage, the glutathione S-transferase and the protease were separated by gel filtration chromatography on a Sephadex G-75 column. The overall yield of the protease purification procedure was about 1 mg of protease/liter of culture, and the specific activity was 380 pmol/min.micrograms of enzyme. Like other retroviral proteases, the MMTV enzyme was active as a dimer, showed maximum activity at pH between 4 and 6, and could be inhibited by pepstatin A and a phosphinic acid derivative HIV-1 protease inhibitor. Enzymatic characterization of this protease reveals its broad specificity, showing a clear preference for the oligopeptide substrate mimicking the cleavage site at the amino-terminal end of the capsid protein (kcat/Km = 9725.5 M-1.s-1). The chimeric protein was also an active dimer and showed a similar Km (17 microM) for such an oligopeptide, although its kcat was about 10 times smaller. Autocatalytic processing of the MMTV protease was observed after expression of clones containing the natural cleavage site, as it occurs at the amino-terminal end of the viral protease, instead of the thrombin-sensitive sequence.

Amino Acid Sequence↗
PubMed1991

Use of a triple protease-deficient mutant of Bacillus subtilis as a host for secretion of a B. subtilis cellulase and TEM beta-lactamase.

The mature portion of the TEM beta-lactamase (BLA) gene (bla) derived from pBR322 was fused with the promoter and signal region of Bacillus subtilis cellulase (BSC) gene (bsc), and the productivity was compared with that of the cloned native bsc gene, using a wild-type B. subtilis strain and a strain deficient in three proteases (i.e., extracellular serine protease, extracellular neutral protease, and the major intracellular serine protease) as hosts. The effects of the sen, sacQ, and prtR genes, carried on the same plasmids, were tested as for the productivities of BSC and BLA. The production of BSC was increased 9-fold by using the combination of the triple-protease deficient strain and the sacQ gene, compared with that by using the wild-type strain as a host, and no degradation of BSC was observed in the triple-protease deficient strain. On the other hand, though the production of the BSC-BLA fusion protein increased 2.5-fold in the triple-protease deficient strain, the BLA activity was decreased after the cell reached the stationary phase of growth, possibly due to some proteolysis. These observations show different sensitivity of secretary proteins to cellular proteases, and suggest that BLA is decomposed by remaining minor proteases.

Amino Acid Sequence↗
PubMedDate not supplied

[The serine proteases and their function in neuronal death processes].

AIMS: In this review we analyse the role played by the serine proteases in the nervous system and we focus on the role they play in degenerative processes. DEVELOPMENT: These proteolytic enzymes, together with the caspases, play a vital role in the processes regulating cell functioning, both in the development stages and following the response to a harmful stimulus. This family of proteases includes the granzymes and thrombin (TR). The former, which are closely related to proteases I and II and cathepsin G, are situated in the cytoplasmic granules of the activated T lymphocytes, together with other proteins such as perforin or cytolysin. Granzymes A and B are linked to degenerative processes. These enter the target cells thanks to the action of perforin and once inside they are translocated to the nucleus. Granzyme A has been isolated and identified as the agent responsible for the immediate and complete retraction of neurites in different models. Its physiological substrates include fibronectin, type IV collagen and the proteoglycans. Granzyme B is characterised by its being a cysteine protease with substrates such as prointerleukin 1 beta, TR receptor and poly(ADP ribose) polymerase. The family of TR type proteases includes proteases such as TR itself, plasmin, kallikrein, urokinase plasminogen activator and tissue plasminogen activator. TR is considered to be an early modulator in damaged tissues which acts as an extracellular signal of death, leading to the activation of intracellular mechanisms that appear to be mediated by calcium. Serine protease activity is regulated by endogenous inhibitors, such as plasminogen activator inhibitor, protease nexin 1 and neuroserpin. CONCLUSIONS: Upsets in the protease inhibitor balance are crucial in the processes involved in the neuronal plasticity and death induced by ischemia in the brain and by excitotoxins.

Animals↗
PubMed1988

In vivo and in vitro autoprocessing of human immunodeficiency virus protease expressed in Escherichia coli.

The viral-specific protease of human immunodeficiency virus (HIV) has been expressed as a lacZ-protease fusion protein. This fusion protein contains protease cleavage sites at the gag/protease and protease/reverse transcriptase junctions and undergoes autoprocessing in vivo when expressed in Escherichia coli. The purified lacZ-protease fusion protein precursors also exhibit autoproteolytic activity in vitro. One cleavage product of the autoprocessing reactions is a 10-kDa protein that cross-reacts with peptide antisera prepared against the putative protease sequence. Consistent with the notion that HIV protease is an acid protease, its autoproteolytic activity is inhibited in alkaline buffers and by pepstatin A. The in vivo and in vitro autocleavage assays for HIV protease together with the overproduction of the protease should facilitate design and testing of therapeutic agents that inhibit gag-pol polyprotein processing and HIV virion maturation.

DNA Restriction Enzymes↗
PubMed1985

Preferential degradation of the oxidatively modified form of glutamine synthetase by intracellular mammalian proteases.

Four intracellular proteases partially purified from liver preferentially degraded the oxidatively modified (catalytically inactive) form of glutamine synthetase. One of the proteases was cathepsin D which is of lysosomal origin; the other three proteases were present in the cytosol. Two of these were calcium-dependent proteases with different calcium requirements. The low-calcium-requiring type (calpain I) accounted for most of the calcium-dependent activity of both mouse and rat liver. The calcium-independent cytosolic protease, referred to as the alkaline protease, has a molecular weight of 300,000 determined by gel filtration. Native glutamine synthetase was not significantly degraded by the cytosolic proteases at physiological pH, but oxidative modification of the enzyme caused a dramatic increase in its susceptibility to attack by these proteases. In contrast, trypsin and papain did degrade the native enzyme and the degradation of modified glutamine synthetase was only 2- to 4-fold more rapid. Adenylylation of glutamine synthetase had little effect on its susceptibility to proteolysis. Although major structural modifications such as dissociation, relaxation, and denaturation also increased the rate of degradation, the oxidative modification is a specific type of covalent modification which could occur in vivo. Oxidative modification can be catalyzed by a variety of mixed function oxidase systems present within cells and causes inactivation of a number of enzymes. Moreover, the presence of cytosolic proteases which recognize the oxidized form of glutamine synthetase suggests that oxidative modification may be involved in intracellular protein turnover.

Animals↗
PubMed1988

[Characteristics of the protease activity of Vibrio cholerae strains and mutants with various biological properties].

The study of 65 V. cholerae strains and mutants revealed that protease activity was high in choleragenic strains and mostly low, sometimes even not manifested, in noncholeragenic strains. The use of inhibitors made it possible to determine three types of protease. Choleragenic strains were found to possess all three types of protease, while in noncholeragenic strains only protease of type 1 was detected in very rare cases. In noncholeragenic hemolytic strains and mutants protease of type 3 and in nonhemolytic strains protease of type 2 were mainly detected. Proteases of types 1 and 3 were thermolabile, and protease of type 2 was thermostable. Proteases of types 1 and 2 were found to be correlatively linked with the choleragenicity of V. cholerae and with a number of its properties which determine the pathogenicity of this infective agent.

Cholera Toxin↗
PubMed1988

Proteases secreted by transforming schistosomula of Schistosoma mansoni promote resistance to killing by complement.

Early events in the transformation of schistosomula of Schistosoma mansoni include shedding of the glycocalyx and conversion of the parasite from sensitive to resistant to complement-mediated killing. This is accompanied by a release of proteolytic activity which occurs at the same rate as the first two phenomena and is also complete within 1 h of culture at 37 degrees C in defined synthetic medium. Two serine proteases, of 28 kDa and a 60 kDa, were purified to homogeneity from the culture medium of transforming schistosomula; the purification steps and the initial characterization of these proteases are reported elsewhere. Both proteases accelerated the release of surface molecules from the schistosomula; however, the effect of the 28-kDa protease was much more pronounced. Qualitative analysis of the material cleaved from the schistosomula by the purified proteases on SDS-PAGE revealed a fragmentation pattern identical with that of the material shed spontaneously from transforming schistosomula. This strongly suggests that the 28-kDa and 60-kDa proteases contribute physiologically to the release of the schistosomular surface molecules including the high Mr glycocalyx. The activity of the two proteases was inhibited by PMSF. Freshly transformed schistosomula treated shortly with the purified 28-kDa protease produced a lower C consumption and became more refractory to C killing. Both consumption and killing were mediated by the alternative pathway of C in the absence of antibodies. These results postulate a role for proteases secreted by transforming schistosomula in the release of schistosomular surface molecules which activate C. This may serve as an escape mechanism from C damage employed by transforming schistosomula.

Animals↗
PubMed1985

A novel IgA protease from Clostridium sp. capable of cleaving IgA1 and IgA2 A2m(1) but not IgA2 A2m(2) allotype paraproteins.

Three bacterial strains of Bifidobacterium and Clostridium sp. from patients with inflammatory bowel disease (I.B.D.) and Streptococcus pneumoniae from a patient with pneumonia were identified to produce extracellular proteases cleaving IgA into Fab and Fc fragments. Although the proteases from the Bifidobacterium and the Streptococcus pneumoniae showed the characteristics of typical IgA1 proteases, cleaving the IgA of only the IgA1 subclass, the protease from Clostridium sp. revealed a dual substrate specificity, in that it cleaved both IgA1 and IgA2 of the A2m(1) allotype. The latter protease, however, did not show any activity with respect to the IgA2 of the A2m(2) allotype. Fc fragments isolated from the IgA1 and the IgA2 A2m(1) by digestion with the Clostridium sp. protease were identified to have an identical amino terminal residue of valine. The site of cleavage in both the alpha 1 and the alpha 2 of A2m(1) by the protease was assumed to be an identical peptide bond at Pro(221)-Val(222), which is a common one present just before the hinge of both the alpha 1 and the alpha 2 of the A2m(1) but not of the alpha 2 of the A2m(2). The protease was sensitive to ethylene-diamino tetraacetic acid, a chelating agent, similar to other already reported IgA1 proteases.

Bacterial Infections↗
PubMed1983

Characteristics, isolation and role in the infectious process of Pseudomonas aeruginosa protease.

Pseudomonas aeruginosa produces the extracellular enzyme protease, which plays an important role in the development of the infectious process caused by this microorganism. Protease is produced in three types, I, II and III, with protease II being responsible for 75% of the total proteolytic activity of protease. The molecular mass of protease II has been determined by different methods; the values obtained are 23000 and 39500. This discrepancy may be associated with an autodigestion of the enzyme or with the presence in the periplasm of its producer of a nonactive precursor whose activation may lead to a change in the molecular mass. Pseudomonas aeruginosa protease is capable of cleaving high-molecular proteins into low-molecular ones, which are taken up by the microbial cell and serve as a source of nutrition. When injected into the bloodstream of animals, purified protease produces haemorrhagic lesions in internal organs; its subcutaneous injection provokes haemorrhage in the skin and subcutaneous tissues. Manifestation of high P. aeruginosa virulence on a model of burnt mouse skin requires that not only exotoxin A but also protease be produced. The protease is immunogenic and has, in toxoid form, been used experimentally in a multicomponent vaccine.

Animals↗
PubMed1980

IgA1 proteases from Haemophilus influenzae, Streptococcus pneumoniae, Neisseria meningitidis, and Streptococcus sanguis: comparative immunochemical studies.

IgA1 proteases from H. influenzae, N. meningitidis, S. pneumoniae, and S. sanguis were compared with respect to site of cleavage in the IgA1 molecule and EDTA sensitivity. Proteases from S. sanguis and S. pneumoniae cleaved the Pro (227)-Thr (228) bond within the hinge region of the alpha 1 chain and were inhibited by EDTA. H. influenzae IgA1 protease cleaved the Pro (231)-Ser (232) peptide bond. The activity of IgA1 proteases from H. influenzae and N. meningitidis was unaffected by EDTA. Purified and denatured alpha 1 chain was cleaved only in the hinge region. Other component chains of secretory IgA (secretory component, light and J chains) were not susceptible. In addition to IgA1 protease, S. pneumoniae released exo- and endoglycosidases that removed a considerable portion of carbohydrate side chains of IgA1; this activity was absent from crude IgA1 protease preparations of the other three bacterial species. Association in vitro of polymeric IgA1 with SC did not inhibit the degradation of IgA1 proteases. The considerable resistance of secretory IgA to cleavage by IgA1 proteases may be explained in part by the presence of IgA1 protease-neutralizing antibodies in secretory IgA.

Amino Acid Sequence↗
PubMed1994

Purification of the extracellular acidic proteases of Dichelobacter nodosus.

Dichelobacter nodosus, a Gram negative obligate anaerobe and causative organism of ovine footrot, secretes a family of extracellular acidic serine proteases with pI's in the range of 5.2 to 5.6, and a basic serine protease with a pI of approximately 9.5. Four acidic proteases (V1, V2, V3 and V5) from virulent and five acidic proteases (B1 to B5) from benign strains of D. nodosus were purified by chromatography on Sephadex G-100 and DEAE-Sepharose CL-6B. Proteases V2, V5 and B5 were found to yield two forms (a and b) on purification which probably arise from limited autolysis of the parent molecule. Amino acid compositions, peptide profiles produced on autolysis and apparent Mr on SDS-PAGE of proteases V1-V3 showed that they were similar to each other and to proteases B1 to B4, and that these proteases were clearly distinct from proteases V5 and B5, which were found to be identical.

Amino Acid Sequence↗