Proteinase inhibitors as antileishmanial agents

In vitro effects of cysteine protease inhibitors on Trichomonas foetus-induced cytopathic changes in porcine intestinal epithelial cells

OBJECTIVE To investigate the effects of specific cysteine protease (CP) inhibitors on cytopathic changes to porcine intestinal epithelial cells induced by Tritrichomonas foetus isolated from naturally infected cats. SAMPLE T foetus isolates from 4 naturally infected cats and nontransformed porcine intestinal epithelial cells. PROCEDURES T foetus isolates were treated with or without 0.1 to 1.0mM of the CP inhibitors antipain, cystatin, leupeptin, and chymostatin and the vinyl sulfone inhibitors WRR-483 and K11777. In-gel gelatin zymography was performed to evaluate the effects of these inhibitors on CP activity of T foetus isolates. Each treated or untreated isolate was also cocultured with monolayers of porcine intestinal epithelial cells for 24 hours, and cytopathic effects of T foetus were evaluated by light microscopy and crystal violet spectrophotometry. RESULTS Results of in-gel gelatin zymography suggested an ability of WRR-483, K11777, and cystatin to target specific zones of CP activity of the T foetus isolates. These inhibitors had no effect on T foetus growth, and the cytopathic changes to the intestinal epithelium induced by all 4 T foetus isolates were significantly inhibited. CONCLUSIONS AND CLINICAL RELEVANCE This study revealed that certain protease inhibitors were capable of inhibiting regions of CP activity (which has been suggested to cause intestinal cell damage in cats) in T foetus organisms and of ameliorating T foetus-induced cytopathic changes to porcine intestinal epithelium in vitro. Although additional research is needed, these inhibitors might be useful in the treatment of cats with trichomonosis.

Leishmania mexicana: Identification and characterization of an aspartyl proteinase activity

An aspartyl proteinase activity was detected in the soluble fraction (SF) of Leishmania mexicana promastigotes by the use of the synthetic substrate benzoyl-Arg-Gly-Phe-Phe-Leu-4-methoxy-beta-naphthylamide selective for Cathepsin D like aspartyl-proteinases. This peptide was hydrolyzed with an apparent K(m) of 2.3+/-0.3 microM. The classic inhibitor of aspartyl-proteinases, diazo-acetyl-norleucinemethylester (DAN) inhibited the proteolytic activity with an IC(50) of 400 microM. The soluble fraction degraded (in absence of thiol groups) human fibrinogen with a specific activity of 533 U/mg protein. When tested for the ability to inhibit the "in vitro" proliferation of L. mexicana promastigotes, DAN showed concentration dependent anti-proliferative effects with a LD(50) of 466 microM at 48 h, with a significant fall in this value to 22 microM after 72 h. This is the first characterization of an aspartyl-proteinase activity in Leishmania, calling for further studies directed towards the physiologic role of these enzymes in the parasite. The anti-proliferative effect of its inhibition makes this enzyme a putative new target for the development of leishmanicidal drugs.

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)

A cathepsin L-like cysteine proteinase gene from the protozoan parasite, Cryptobia salmositica

The present study describes the identification of a cathepsin L-like cysteine proteinase gene (CYS) from the hemoflagellate Cryptobia salmositica. Genomic DNA sequence of cysteine proteinase was obtained by genome walking using degenerate primers. Specific primers were designed to amplify the cDNA of cysteine proteinase from mRNA by rapid amplification of cDNA ends-PCR. The open reading frame of CYS is 1,329 bp, with 443 deduced amino acids. Based on the sequence analysis, cysteine proteinase of C. salmositica is similar to the cathepsin L-like cysteine proteinase of kinetoplastid parasites such as Leishmania spp. and Trypanosoma spp. The identification of CYS proteinase gene could help to design cysteine proteinase specific inhibitors. Further studies are required to characterize the complete genomic organization of the cysteine proteinase.

Aromatic diamidines as antiparasitic agents

Parasitic infections are widespread in developing countries and frequently associated with immunocompromised patients in developed countries. Consequently, such infections are responsible for a significant amount of human mortality, morbidity and economic hardship. A growing consensus has identified the urgent need for the development of new antiparasitic compounds, mostly due to the large number of drug-resistant parasites and the fact that currently available drugs are expensive, highly toxic, require long treatment regimens and frequently exhibit significantly reduced activity towards certain parasite strains and evolutive stages. In this context, the activity of aromatic diamidines has been explored against a widespread range of micro-organisms, and the authors' present aim is to review the current status of chemotherapy with these compounds against human parasitic infections.

Molecular cloning and characterization of Cathepsin B from a scuticociliate, Uronema marinum

A cDNA encoding cathepsin B was cloned from the scuticociliate, Uronema marinum, which invades the olive flounder, Paralichthys olivaceus, leading to high mortalities in culturing fish. The full-length scuticociliate cathepsin B (ScCtB) gene contains an open reading frame of 1053 base pairs encoding 350 amino acids. A homology search revealed that ScCtB shares sequence identity with several piscine cathepsin Bs (48%-45%). The protein of ScCtB from U. marinum extracts was purified 12.8-fold by a one step purification process using a DEAE-Sephagel high performance liquid chromatography (HPLC) column. It had a molecular mass of 30 kDa, as estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting, which was consistent with predicting molecular mass of mature protein (29.2 kDa) of ScCtB. The protease activity of the ScCtB enzyme was demonstrated by electrophoresis in a gelatin-acrylamide copolymerized gel. Its activity was quantified by cleaving a synthetic fluorogenic peptide substrate, Z-arginyl-arginyl-7-amido-4-methylcoumarin (Z-Arg-Arg-AMC). The optimum pH for the protease activity was 5.5. Typical of cysteine proteases, the enzyme was inhibited by trans-epoxysuccinyl-L-leucyl-amido(4-guanidino)butane (E-64) and leupeptin.

Cysteine proteinases of parasitic protozoa

Proteinases are involved with many processes in living organisms. In recent years, there has been increasing interest in elucidating the functions the enzymes perform in parasites. These studies have revealed that one class of proteinases, the cysteine proteinases, predominates in many parasitic protozoa. In this article Mick North, Jeremy Mottram and Graham Coombs review what is known about the cysteine proteinases of parasitic protozoa and discuss the approaches being pursued in attempts to design antiparasite drugs based on inhibitors or substrates of these enzymes.

The use of metal chelate affinity chromatography on the isolation of Leishmania chagasi promastigote hydrophobic proteinases

In this work, we have assessed the possibility of isolating metalloproteinase fractions from infective Leishmania chagasi promastigotes. Our strategy was the association of the Triton X-114 method with iminodiacetic chromatography enriched with Zn2+. Thus, by using acid conditions, it was possible to isolate two fractions containing two polypeptides, 59 and 63 kDa. The enzymatic activity assay indicated that the two fractions and the two polypeptides had proteinase activities. In addition, it was proposed that those proteinase activities were affected by the presence of 1,10-phenanthroline, a metalloproteinase inhibitor. With this gentle chromatography strategy proposed it is possible to obtain metalloproteinases from L. chagasi in folding that preserve the enzyme activity. This is important for further studies on pathological complications observed in visceral leishmaniasis.

Cloning and characterisation of a cysteine proteinase gene expressed in amastigotes of Leishmania (L.) amazonensis

The present study describes the cloning and characterisation of a gene encoding a cysteine proteinase isoform, Llacys1, expressed in amastigote forms of Leishmania (L.) amazonensis. Recombinant clones containing the Llacys1 gene were isolated from genomic DNA by PCR amplification and screening of an amastigote cDNA library. Sequence analysis of the Llacys1 gene showed a high identity to sequence of Leishmania (L.) pifanoi Lpcys1, Leishmania (L.) major cpa, Leishmania (L.) mexicana LCPa, and Leishmania (L.) chagasi Ldccys2. The Llacys1 gene is present in a single copy per L. (L.) amazonensis haploid genome and was mapped on a chromosome of approximately 700 kb. Two transcripts of the Llacys1 gene were identified, one of 2.4 kb transcribed in both forms of L. (L.) amazonensis, and another of 1.6 kb weakly expressed in amastigotes. Related forms of Llacys1 gene exist in other species of Leishmania genus, including L. (L.) major, L. (L.) mexicana, L. (L.) chagasi and Leishmania (V.) braziliensis. The Llacys1 expression in Escherichia coli was obtained when the nucleotide sequence corresponding to the signal sequence was deleted, suggesting that this signal sequence was recognised by Escherichia coli and cleaved, generating a truncated protein.

Cellular trafficking in trypanosomatids: a new target for therapies?

Pathogenic trypanosomatids cause a plethora of diseases marked by the lack of efficient vaccines and therapies. As a consequence, studies are being conducted that are geared towards the understanding of basic mechanisms and various biological aspects of these parasites that might be used as targets for new developments in these areas. One such aspect is the understanding of specific cellular trafficking mechanisms that might be attacked with the intention of disease control. In this paper, we give an overview of our current knowledge of cellular targeting mechanisms in trypanosomatids, with special emphasis on our data related to lysosomal targeting of cysteine proteinases in Leishmania.

The Leishmania mexicana proteasome

As a start to understanding the importance of intracellular proteolysis in the protozoon Leishmania mexicana, the parasite proteasome has been purified and characterised. The L. mexicana proteasome is similar to proteasomes from other eukaryotes. It is soluble, and the 20S form has a mass of around 670 kDa, composed of at least 10 distinct subunits in the 22 to 32 kDa size range. The molecular mass of the L. mexicana proteasome increases to 1200 kDa in the presence of adenosine-5'-triphosphate, consistent with there being a 26S proteasome in the parasite. The purified 20S proteasome has activity towards substrates with hydrophobic, basic and acidic P, residues, and is sensitive to a range of peptide aldehyde inhibitors, as well as the proteasome-specific inhibitor lactacystin. The peptide aldehydes are able to arrest parasite growth in vitro with the same relative effectiveness as against the purified proteasome activity. The parasite population arrests with an increased 4N DNA content, indicating that, in part, the essential nature of the proteasome for L. mexicana proliferation is due to a role in the parasite cell cycle. Surprisingly, lactacystin is a relatively inefficient inhibitor of L. mexicana growth in vitro.

Molecular cloning, characterization and overexpression of two distinct cysteine protease cDNAs from Leishmania donovani chagasi

We have cloned and characterized two distinct cysteine protease cDNAs from Leishmania donovani chagasi. One of the cDNAs, Ldccy2, was isolated from a cDNA library prepared from total promastigote RNA while the other cDNA, Ldccys1, was isolated from a cDNA library prepared from total amastigote RNA. Ldccys2 has an open reading frame of 471 amino acids and Ldccys1 has an open reading frame of 447 amino acids. Comparison of the predicted protein sequences of the two distinct cysteine proteases with those of cysteine proteases from Leishmania pifanoi, a member of the L. mexicana complex, showed that the cysteine proteases from the two species of Leishmania are similar in their protein sequences. Each of the two cDNAs is distinct in genomic arrangement and chromosome location. Ldccys1 belongs to a family of cysteine proteases encoded by tandemly organized genes located on chromosome 7 while Ldccys2 appears to be a single cysteine protease gene located on chromosome 10. The organization of the two families of cysteine protease genes in L. donovani donovani was also found to be similar. In this species, the Lddcys1 genes are located on chromosome 5 while the Lddcys2 gene is located on chromosome 8. The Ldccys1 genes are expressed abundantly in the amastigotes recovered from infected hamsters, but at a very low level in the promastigote stage of development. On the other hand, the Ldccys2 gene is expressed both in the promastigote and amastigote stages. We have overexpressed the two cDNAs of cysteine proteases in Leishmania cells and the over-produced cysteine proteases are biologically active and are inhibited by cysteine protease inhibitors. Furthermore, the over-produced and indigenous amastigote specific cysteine protease, Ldccys1, reacted with polyclonal antibodies raised against this protein.

Leishmania major: comparison of the cathepsin L- and B-like cysteine protease genes with those of other trypanosomatids

Cysteine proteases play important roles in the pathogenesis of several parasitic infections and have been proposed as targets for the structure-based strategy of drug design. As a first step toward applying this strategy to design inhibitors as antiparasitic agents for leishmaniasis, we have isolated and sequenced the full-length clones of two cysteine protease genes from Leishmania major. One of the genes is structurally similar to the cathepsin L-like family and the other is similar to the cathepsin B-like family of cysteine proteases. The L. major cathepsin L-like sequence has a proregion that shares high sequence similarity with other cathepsin L sequences but not cathepsin B sequences and has a proline/threonine-rich C-terminal extension. The cathepsin L-like gene occurs in multiple copies, whereas there may be only one copy of the cathepsin B-like gene. Northern blot analyses show that both genes are expressed in the promastigote and amastigote stages, and pulse field gel electrophoresis revealed that the cathepsin L- and B-like genes are each found on two nonhomologous chromosomes. The L. major L-like amino acid sequence is 75% identical to the L. mexicana sequence, 74% identical to the L. pifanoi sequence, 47% identical with the Trypanosoma cruzi sequence, 47% identical with the T. congolense sequence, and 45% identical with the T. brucei sequence. L. major is one of two trypanosomatid species for which a cathepsin B-like gene has been identified and sequenced; its amino acid sequence is 82% identical to the one from L. mexicana. Tree inference based on distance and parsimony methods of kinetoplastid cathepsin L proteins yielded independent support for phylogenetic hypotheses inferred from analyses of ribosomal RNA genes. Because the cathepsin L locus has a high level of phylogenetic signal with respect to trypanosomatid taxa, this locus has great potential utility for investigating the evolutionary history of trypanosomatids and related organisms.

Evidence from disruption of the lmcpb gene array of Leishmania mexicana that cysteine proteinases are virulence factors

The mammalian form of the protozoan parasite Leishmania mexicana contains high activity of a cysteine proteinase (LmCPb) encoded on a tandem array of 19 genes (lmcpb). Homozygous null mutants for lmcpb have been produced by targeted gene disruption. All life-cycle stages of the mutant can be cultured in vitro, demonstrating that the gene is not essential for growth or differentiation of the parasite. However, the mutant exhibits a marked phenotype affecting virulence-- its infectivity to macrophages is reduced by 80%. The mutants are as efficient as wild-type parasites in invading macrophages but they only survive in a small proportion of the cells. However, those parasites that successfully infect these macrophages grow normally. Despite their reduced virulence, the mutants are still able to produce subcutaneous lesions in mice, albeit at a slower rate than wild-type parasites. The product of a single copy of lmcpb re-expressed in the null mutant was enzymatically active and restored infectivity toward macrophages to wild-type levels. Double null mutants created for lmcpb and lmcpa (another cathepsin L-like cysteine proteinase) have a similar phenotype to the lmcpb null mutant, showing that LmCPa does not compensate for the loss of LmCPb.

Distribution of parasite cysteine proteinases in lesions of mice infected with Leishmania mexicana amastigotes

It is well established that Leishmania mexicana amastigotes contain large amounts of cysteine proteinases in their extended lysosomes. In this study it is shown that the cell-free supernatant of homogenized lesion tissue from infected mice contains large amounts of acid proteinases. The majority of this enzymatic activity also corresponds to cysteine proteinases from L. mexicana amastigotes. Immunoelectron microscopy of mouse lesion sections suggests, that frequently amastigotes lyse and release lysosomal cysteine proteinases into the parasitophorous vacuole of infected macrophages. The cysteine proteinases are also found extracellularly in the tissue presumably as a result of macrophage rupture and appear to persist in the lesion tissue, where they may damage host cells and the extracellular matrix.

Null mutants for the lmcpa cysteine proteinase gene in Leishmania mexicana

The parasitic protozoon Leishmania mexicana possesses an abundance of developmentally regulated cathepsin L-like cysteine proteinases expressed at highest levels in amastigotes. We recently characterised lmcpa, a single-copy gene encoding one such proteinase, LmCPa, which differs from other homologues by possessing a 3-amino-acid insertion at the amino terminal of the predicted mature proteinase. To investigate the role of LmCPa in L. mexicana, we used gene-targeting of promastigotes with hygromycin- and phleomycin-resistance markers to generate null mutants by disrupting sequentially both alleles of lmcpa. The promastigote null mutants did not differ significantly from wild-type L. mexicana in growth rate or morphology and could differentiate to metacyclics and the amastigote-like form, both of which could infect the J774G8 macrophage-like cell line. The null mutant amastigote-like form obtained from the J774G8 cells could also establish rump lesions in CBA mice. By these criteria, therefore, LmCPa appears to be non-essential although there is the possibility that LmCPa could be required during development in the sandfly, a stage not analysed here. The apparent redundancy of LmCPa in amastigotes may be due to the presence of other cysteine proteinases and has implications for the choice of candidate targets for rationally designed anti-leishmanial drugs.

Cathepsin B-like cysteine proteases of Leishmania mexicana

A group of Leishmania mexicana cysteine proteases that differ from those previously found in this protozoon are described. The enzymes characteristically have a preference for peptidyl substrates with a phenylalanyl-valyl-arginyl moiety, do not hydrolyse gelatin in substrate-sodium dodecyl sulphate polyacrylamide gels, are stimulated by thiol-reducing agents and are sensitive to inhibitors specific for cysteine proteases. They have unusual solubility properties that indicate that the enzymes are amphiphilic proteins. Two of the cysteine proteases have been purified from L. mexicana amastigotes and shown to have molecular masses of 31 and 33 kDa. Their N-terminal amino acid sequences are very similar and show high homology to the mammalian cysteine protease, cathepsin B.

Developmental life cycle of Leishmania--cultivation and characterization of cultured extracellular amastigotes

The biochemistry and immunology of Leishmania promastigotes has been extensively studied; this is due primarily to the facility with which this stage, in contrast to the amastigotes stage, can be maintained in axenic culture. Several attempts to axenically culture lines of Leishmania amastigotes have been reported in the literature. This paper summarizes methods of adaptation (low pH, elevated temperature and culture medium) and characterization of several axenic lines of Leishmania amastigotes. Based on morphological, biological, immunological and biochemical evidence, these organisms appear to resemble amastigotes from infected macrophages or tissue. The axenically cultured amastigotes appear to be distinct from shocked (heat, serum deprivation, stressed) Leishmania promastigotes in the plethora of proteins synthesized, growth (multiplication) in culture, and developmental regulation observed. These data suggest that Leishmania organisms have a significant developmental response to certain signals (pH, temperature) mimicking their in vivo macrophage milieu. The response to other environmental parameters characteristic of the host-macrophage remain to be determined. These axenically cultured amastigotes should be of interest for further immunological, biochemical and developmental investigations of the disease-maintaining stage of this parasite.

Identification of two distinct cysteine proteinase genes of Leishmania pifanoi axenic amastigotes using the polymerase chain reaction

A developmentally regulated cysteine proteinase associated with an unique lysosomal organelle, the megasome, has been described for the intracellular amastigotes of the Leishmania mexicana complex; this proteinase appears to be important in the survival of the parasite. Degenerate primers encoding the active sites residues have been used to amplify cysteine proteinase cDNA sequences from axenically cultured amastigotes of Leishmania pifanoi, a member of the L. mexicana complex. Based on sequence data, two distinct genes (Lpcys1 and Lpcys2) were identified. Although both genes are preferentially transcribed in the amastigote stage, each is distinct in genomic arrangement and chromosome location, with Lpcys2 showing evidence for the presence of 8-20 tandemly arrayed copies and mRNA levels 10-fold higher than Lpcys1. Related forms of the Lpcys1 and Lpcys2 genes exist in other species of the genus Leishmania, including Leishmania braziliensis, Leishmania major and Leishmania donovani. The protein sequence of an abundant immunoaffinity purified amastigote cysteine proteinase (A-2) is identical to that predicted for the product of Lpcys2; immunofluorescence studies show an intracellular pattern/distribution for the A-2 proteinase consistent with a putative megasomal association. The DNA sequence of a genomic copy of Lpcys2 predicts a C-terminal extension for the proteinase; comparative sequence analyses of the C-terminal extensions found for Trypanosoma cruzi and Trypanosoma brucei reveal the selective conservation of cysteine, as well as proline and glycine residues, suggesting that conservation of folding and secondary structure may be required for biological function.

Trichomonas vaginalis surface proteinase activity is necessary for parasite adherence to epithelial cells

The role of cysteine proteinases in adherence of Trichomonas vaginalis NYH 286 to HeLa and human vaginal epithelial cells was evaluated. Only pretreatment of trichomonads, but not epithelial cells, with N-alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK), an inhibitor of trichomonad cysteine proteinases, greatly diminished the ability of T. vaginalis to recognize and bind to epithelial cells. Leupeptin and L-1-tosylamide-2-phenylethyl chloromethyl ketone, other cysteine proteinase inhibitors, also decreased T. vaginalis cytadherence. Parasites incubated with TLCK and washed extensively still did not adhere to cells at levels equal to those seen for control trichomonads treated with phosphate-buffered saline or culture medium alone. Exposure of TLCK-treated organisms with other cysteine proteinases restored cytadherence levels, indicating that proteinase action on the parasite surface is prerequisite for host cell attachment. Concentrations of TLCK which inhibited cytadherence did not alter the metabolism of T. vaginalis, as determined by metabolic labeling of trichomonad proteins; the protein patterns of T. vaginalis in the presence and absence of TLCK were identical. Kinetics of TLCK-mediated inhibition of cytadherence of other T. vaginalis isolates with different levels of epithelial-cell parasitism were similar to the concentration-dependent inhibition seen for isolate NYH 286. Incubation of TLCK-treated, washed organisms in growth medium resulted in regeneration of adherence. Finally, treatment of T. vaginalis organisms with proteinase inhibitors for abrogation of cytadherence effectively rendered the trichomonads unable to kill host cells, which is consistent with the contact-dependent nature of host cytotoxicity. These data show for the first time the involvement of T. vaginalis cysteine proteinases in parasite attachment to human epithelial cells. These results have implications for future pharmacologic intervention at a key step in infection.

Inhibition of Leishmania amastigote growth by antipain and leupeptin

Antipain and leupeptin were found to be potent inhibitors of the growth of Leishmania mexicana mexicana amastigotes in explanted mouse unstimulated peritoneal macrophages. Antipain at 100 mg l-1 reduced eight-fold the percentage of macrophages infected and to 5% of the control the number of amastigotes present after seven days incubation. At 1 mg l-1, antipain and leupeptin were as effective antileishmanial agents as pentamidine isethionate, all three stopping parasite multiplication over the seven-day incubation.

An analysis of the proteinases of Trichomonas vaginalis by polyacrylamide gel electrophoresis

The proteinases of Trichomonas vaginalis have been analysed by electrophoresis in polyacrylamide gels containing denatured haemoglobin. Seven bands of activity were detected indicating multiple proteinases. All of the enzymes were stimulated by 1 mM dithiothreitol and had inhibitor sensitivities characteristic of cysteine proteinases. The enzymes differed significantly, however, with respect to pH optima and relative sensitivities to inhibitors.