Crystallization and properties of cathepsin B from rat liver

Protective Effects of N-Acetylcysteine and Vitamin E Derivative U83836E on Proteins Modifications Induced by Methanol Intoxication

Methanol is oxidized into the formaldehyde and formate and these processes are accompanied by free radicals' generation. Formaldehyde and free radicals induce chemical modifications of proteins, leading to changes in their structure and function. The aim of this paper has been to evaluate the effect of N-acetylcysteine and vitamin E derivative U83836E on free radicals' generation and protein modifications induced during acute methanol intoxication. U83836E is an analog of alpha-tocopherol and similarly protects cells against oxidative damage. Moreover, this compound has hydrophilic properties and can be dissolved in an aqueous phase of blood and interstitial fluid, and next, membranes readily take it up. This compound belonging to the benzopyran family contains the reactive trolox ring and possesses antioxidant properties. The ESR determination indicates the increase in free radicals' signal 6 and 12 h after intoxication. Methanol ingestion causes a significant decrease in GSH level (by about 35%) and a significant increase in the lipid peroxidation product malondialdehyde (by about 25%). During methanol metabolism the aromatic amino acids of proteins are modified-the amount of carbonyl groups is increased (by about 42%) and fluorescence intensity of tryptophan is statistically decreased (by about 30%). The increase (by about 200%) in bityrosine fluorescence is also observed. Moreover, a significant decrease in free sulphydryl (by about 40%) and amino groups (by about 30%) in liver proteins is observed during intoxication. This is accompanied by the loss of lysosomal protease-cathepsin B activity (by about 25%). N-acetylcysteine (in dose 150 mg/kg body weight) and U83836E (in dose 10 mg/kg body weight) prevent free radicals' generation to a similar degree. U83836E protects membrane phospholipids against peroxidation a little stronger than N-acetylcysteine (concentration of MDA is decreased by 9 to 20% in the U83836 group and by 7 to 14% in the N-acetylcysteine group compared to methanol group). However after treating methanol-intoxicated rats with N-acetylcysteine, the changes in protein modification parameters are significantly smaller than in the group receiving methanol alone and they are a little smaller than after U83836E application. These findings suggest that N-acetylcysteine and to a smaller degree U83836E protect protein from modification in methanol intoxication, which can prevent liver pathologies.

Nobuhiko Katunuma: an outstanding scientist in the field of proteolysis and warm-hearted 'Kendo Fighter' biochemist

Professor Nobuhiko Katunuma is well known for his outstanding contribution to the understanding of proteolysis in general and cysteine proteinases and their inhibitors in mammals. In fact, he is a world pioneer in the field. In 1963, he started his highly successful scientific career as a Professor at the Institute for Enzyme Research, the University of Tokushima. During the initial 30 years of his career, he was interested in vitamin B6 metabolism and discovered the acceleration of turnover rates of pyridoxal enzyme in apoprotein formation. After this period, his interest expanded to lysosomal cystein proteinases and their endogenous inhibitors. After determining the crystal structure of human cathepsin B, he generated a series of chemically synthesized specific inhibitors of cathepsins. These inhibitors are currently used throughout the world and some of them have been applied therapeutically in various diseases. During his career and even at present, Professor Katunuma has been studying Biochemistry in Medicine and also practicing to become a 'Kendo sword fencing Fighter'.

Posttranslational processing and modification of cathepsins and cystatins

Cathepsins are an essential protease family in all living cells. The cathepsins play an essential roles such as protein catabolism and protein synthesis. To targeting to various organella and to regulate their activity, the post translational-processing and modification play an important role Cathepsins are translated in polysome as the pre-pro-mature forms. The pre-peptide is removed cotranslationally and then translocated to Golgi-apparatus and the pro-part is removed and the mature-part is glycosylated, and the mature-part is targeted into the lysosome mediated by mannose-6-phosphate signal and the mature-part is bound with their coenzymes. The degradation of the mature-part is started by the limited proteolysis of the ordered nicked bonds to make hydrophobic peptides. The peptides are incorporated into phagosome or proteasome after ubiquitinated and are degrade into amino-acids. Cystatins are endogenous inhibitors of cathepsins. Cystatin α which is only located in skin is phosphorylated at the near C-terminus by protein kinase-C, and the phosphorylate-cystatin α is incorporated into cornified envelope and conjugated with filaggrin-fiber by transglutaminase to form the linker-fiber of skin. The cystatin α is modified by glutathione or make their dimmer, and they are inactive. Those modifications are regulated by the redox-potential by the glutathione.

Identification of essential residues of CTLA-2alpha for inhibitory potency

To identify functionally essential sequences and residues of CTLA-2alpha, in vitro mutagenesis was carried out. The coefficient of inhibition (K(i)) was determined towards rabbit cathepsin L using Z-Phe-Arg-MCA as the substrate. Recombinant CTLA-2alpha inhibited the enzyme potently (K(i) = 15 nM). A truncated mutant, lacking the N- and C-terminal Ala1-Asp9 and Leu80-Glu109 regions, was also a potent inhibitor (K(i) = 10 nM). Subsequent short deletions in the central region (Asn10-Ser79) showed three functionally essential distinct regions: Asn10-Phe19, His30-Ala44 and Ser55-Ser79. These regions cover sequences corresponding to three helices (alpha1, alpha2 and alpha3) and sequences that interact with the cognate enzyme. Alanine scanning showed that replacement of one of three conserved Trp residues increased the K(i) by 15-20-fold; whereas, replacement of two/three Trp residues at once caused complete loss of potency, as did replacing Cys75 with Ala or Ser. The proteins from wild-type (WT) CTLA-2alpha and mutant C75A were stable overnight when incubated with cathepsin L; whereas, proteins from mutants W12A, W15A and W35A were quickly digested. Incubation of cathepsin L/WT CTLA-2alpha formed a complex; whereas, C75S did not form a complex. Our overall results point to a critical role of W12, W15, W35 and Cys75 residues in CTLA-2alpha.

Oxidative Modifications of Rat Liver Cell Components During Fasciola hepatica Infection

The aim of this paper was to assess the influence of Fasciola hepatica infection on oxidative modifications of rat liver cell components such as proteins and lipids. Wistar rats were infected per os with 30 metacercariae of F. hepatica. Activities and concentrations of liver damage markers were determined in the 4th, 7th, and 10th week postinfection (wpi). A decrease in antioxidant capacity of the host liver, manifested by a decrease in total antioxidant status (TAS), was observed. Diminution of antioxidant abilities resulted in enhanced oxidative modifications of lipids and proteins. F. hepatica infection enhanced lipid peroxidation, which was visible in the statistically significant increase in the level of different lipid peroxidation products such as conjugated dienes (CDs), lipid hydroperoxides (LOOHs), malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE). The level of protein modification markers in the rat liver was also significantly changed and the most intensified changes were observed at seventh week postinfection. Concentration of carbonyl groups and dityrosine was significantly increased, whereas the level of tryptophan and sulfhydryl and amino groups was decreased. Changes in the antioxidant abilities of the liver and in the lipid and protein structure of the cell components resulted in destruction of the function of the liver. F. hepatica infection was accompanied by raising serum activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) as markers of liver damage. A significant decrease in lysosomal as well as in the total activity of cathepsin B during fasciolosis was also observed.

Drosophila CTLA-2-like protein (D/CTLA-2) inhibits cysteine proteinase 1 (CP1), a cathepsin L-like enzyme

In this study, we present a propeptide-like cysteine proteinase inhibitor, Drosophila CTLA-2-like protein (D/CTLA-2), a CG10460 (crammer) gene product, with an amino acid sequence significantly similar to the proregion of Drosophila cysteine proteinase 1 (CP1). Recombinant D/CTLA-2, expressed in E. coli, strongly inhibited Bombyx cysteine proteinase (BCP) with a Ki value of 4.7 nM. It also inhibited cathepsins L and H with Ki values of 3.9 (human liver) and 0.43 (rabbit liver) nM, and 7.8 nM (human liver), respectively. Recombinant D/CTLA-2 exhibited low but significant inhibitory activities to cathepsin B with Ki values of 15 nM (human liver) and 110 nM (rat liver), but hardly inhibited papain. We attempted to purify cysteine proteinases inhibited by D/CTLA-2 from total bodies of adult Drosophila. Recombinant D/CTLA-2 significantly inhibited CP1 with a Ki value of 12 nM, indicating that CP1, a cognate enzyme of D/CTLA-2, is a target enzyme of the inhibitor in Drosophila cells. These results indicate that D/CTLA-2 is a selective inhibitor of cathepsin L-like cysteine proteinases similar to other propeptide-like cysteine proteinase inhibitors such as Bombyx cysteine proteinase inhibitors (BCPI) and cytotoxic T-lymphocyte antigen-2 (CTLA-2). D/CTLA-2 was expressed over the whole life cycle of Drosophila. Strong expression was observed in the garland cells and prothoracic gland in the late stages of embryonic development. These results suggest that D/CTLA-2, implicated in intra- and extra-cellular digestive processes, functions in these tissues by suppressing uncontrolled enzymatic activities of CP1.

Evaluation of serum cathepsin B and D in relation to clinicopathological staging of colorectal cancer

AIM: Proteolytic degradation of the extracellular matrix facilitates cancer invasion and promotes metastasis. The study aims at evaluation of preoperative and postoperative serum cathepsins B and D levels in correlation with selected anatomoclinical features of colorectal cancer.

METHODS: Blood samples were collected from 63 colorectal cancer patients before curative operation of the tumor 10 d later. Blood that was obtained from 20 healthy volunteers, served as a control. The activity of cathepsin B was measured with Bz-DL-arginine-pNA as a substrate at pH 6.0, while cathepsin D activity was determined with urea-denatured hemoglobin (pH 4.0).

RESULTS: The preoperative and postoperative activities of cathepsin B were significantly (P < 0.00001) lower in serum of colorectal cancer patients than in control group. However, postoperative values of this protease were significantly increased in comparison with preoperative ones (P = 0.031). Activity of cathepsin D appeared to be significantly higher in colorectal cancer sera (P < 0.00001) compared with controls. No statistically significant differences between preoperative and postoperative activity of cathepsin D were noted (P = 0.09). We revealed a strong linkage of cathepsins’ levels with lymph node status and pT stage of colorectal cancer.

CONCLUSION: Blood serum activities of cathepsin B and D depend on the time of sampling, tumor size and lymph node involvement. Significantly, increased activity of cathepsin D could indicate a malignant condition of the large intestine. In our work, the serum postoperative decrease of cathepsin B activity appears as an obvious concomitant of local lymph node metastasis-the well-known clinicopathological feature of poor prognosis.

A cathepsin B-like enzyme from mackerel white muscle is a precursor of cathepsin B

A cathepsin B-like enzyme from the white muscle of common mackerel Scomber japonicus was a cysteine protease that hydrolyzed Z-Arg-Arg-MCA, the substrate for cathepsin B. In a partial purified cathepsin B-like enzyme preparation at 4 degrees C left over time, a converted enzyme that hydrolyzes Z-Arg-Arg-MCA and Z-Phe-Arg-MCA appeared in the preparation. The converted enzyme was purified from the cathepsin B-like enzyme, characterized and was identified as mackerel cathepsin B. These results suggested that the mackerel cathepsin B-like enzyme was a precursor of cathepsin B. Mackerel cathepsin B formed in the purified cathepsin B-like enzyme preparation by adding of a small amount of the purified cathepsin B to the preparation. Therefore, mackerel cathepsin B-like enzyme was converted to the mature form of cathepsin B by autoactivation. The conversion of the cathepsin B-like enzyme (molecular mass 60 kDa) to cathepsin B (molecular mass 23 kDa) was detected by immunoblotting by using human anti-(cathepsin B) antibody. The intermediate forms of 40 kDa and 38 kDa were also detected during the conversion.

Defective oligomerization of arylsulfatase a as a cause of its instability in lysosomes and metachromatic leukodystrophy

In one of the most common mutations causing metachromatic leukodystrophy, the P426L-allele of arylsulfatase A (ASA), the deficiency of ASA results from its instability in lysosomes. Inhibition of lysosomal cysteine proteinases protects the P426L-ASA and restores the sulfatide catabolism in fibroblasts of the patients. P426L-ASA, but not wild type ASA, was cleaved by purified cathepsin L at threonine 421 yielding 54- and 9-kDa fragments. X-ray crystallography at 2.5-A resolution showed that cleavage is not due to a difference in the protein fold that would expose the peptide bond following threonine 421 to proteases. Octamerization, which depends on protonation of Glu-424, was impaired for P426L-ASA. The mutation lowers the pH for the octamer/dimer equilibrium by 0.6 pH units from pH 5.8 to 5.2. A second oligomerization mutant (ASA-A464R) was generated that failed to octamerize even at pH 4.8. A464R-ASA was degraded in lysosomes to catalytically active 54-kDa intermediate. In cathepsin L-deficient fibroblasts, degradation of P426L-ASA and A464R-ASA to the 54-kDa fragment was reduced, while further degradation was blocked. This indicates that defective oligomerization of ASA allows degradation of ASA to a catalytically active 54-kDa intermediate by lysosomal cysteine proteinases, including cathepsin L. Further degradation of the 54-kDa intermediate critically depends on cathepsin L and is modified by the structure of the 9-kDa cleavage product.

Hippocampal cholinergic neurostimulating peptides (HCNP)

Neuronal development and differentiation require a variety of cell interactions. Diffusible molecules from target neurons play an important part in mediating such interactions. Our early studies used explant culture technique to examine the factors that enhance the differentiation of septo-hippocampal cholinergic neurons, and they revealed that several components resident in the hippocampus are involved in the differentiation of presynaptic cholinergic neurons in the medial septal nucleus. One of these components, originally purified from young rat hippocampus, is a novel undecapeptide (hippocampal cholinergic neurostimulating peptide; HCNP); this enhances the production of ChAT, but not of AchE. Later experiments revealed that: (1) a specific receptor appears to mediate this effect; (2) NGF and HCNP act cooperatively to regulate cholinergic phenotype development in the medial septal nucleus in culture; and (3) these two molecules differ both in their mechanism of release from the hippocampus and their mechanism of action on cholinergic neurons. The amino acid sequence deduced from base sequence analysis of cloned HCNP-precursor protein cDNA shows that HCNP is located at the N-terminal domain of its precursor protein. The 21 kDa HCNP precursor protein shows homology with other proteins, and it functions not only as an HCNP precursor, but also as a binding protein for ATP, opioids and phosphatidylethanolamine. The distribution and localization of HCNP-related components and the expression of their mRNAs support the notion that the precursor protein is multifunctional. In keeping with its multiple functions, the multiple enhancers and promoters found in the genomic DNA for HCNP precursor protein may be involved in the regulation of its gene in a variety of cells and at different stages of development. Furthermore, several lines of evidence obtained from studies of humans and animal models suggest that certain types of memory and learning disorders are associated with abnormal accumulation and expression of HCNP analogue peptide and/or its precursor protein mRNA in the hippocampus.

MHC class I presentation of an exogenous polypeptide antigen encoded by the murine AIDS defective virus

Peptides derived from endogenous proteins are presented by MHC class I molecules, whereas those derived from exogenous proteins are presented by MHC class II molecules. This strict segregation has been reconsidered in recent reports in which exogenous antigens are shown to be presented by MHC class I molecules in the phagocytic pathway. In this report, the presentation pathway of an exogenously added highly antigenic polypeptide encoded by the murine AIDS (MAIDS) defective virus gag p12 gene is investigated. A 25-mer polypeptide (P12-25) encoded within the gag p12 region of the MAIDS defective virus was found to be effective in stimulating unprimed B6 (H-2b) CD8+ T cells in vitro. The presentation of P12-25 is sensitive to cytochalasin B and D, brefeldin A and gelonin, a ribosome-inactivating protein synthesis inhibitor, but less sensitive or resistant to lactacystin, a highly specific inhibitor of the proteasome. Interestingly, CA-074, a selective inhibitor of cathepsin B, inhibited presentation of the polypeptide, indicating its involvement in the degradation of the P12-25 polypeptide. In fact, when P12-25 was digested with purified cathepsin B in vitro, a highly antigenic 11-mer peptide containing the class I (H-2Db)-binding motif was obtained. Our results favor the phagosome/macropinosome-to-cytosol-to-endoplasmic reticulum (ER)-to-cell surface pathway for exogenous antigens presented by MHC class I molecules. These findings may be relevant to exploiting peptide vaccines that specifically elicit CD8+ T cell immunity in vivo.

Expression of functional recombinant human procathepsin B in mammalian cells

Cathepsin B has been implicated in numerous pathobiological processes. In order to study its interactions with other proteins implicated in these processes, quantities of functional recombinant cathepsin B are needed. Therefore, we expressed recombinant human procathepsin B in mammalian cells (BSC-1 monkey kidney cells and HeLa human cervical carcinoma cells) using a vaccinia virus expression system. The recombinant human procathepsin B appeared to be authentic and expressed in its native conformation as indicated by: (1) N-terminal sequencing; (2) molecular size; (3) processing intracellularly to mature double-chain cathepsin B; (4) in vitro cleavage by pepsin to mature cathepsin B coincident with appearance of activity against a selective synthetic substrate; and (5) substrate/inhibitor profiles. This is the first report of the expression of functional recombinant human procathepsin B in mammalian cells. We also report a single-step immunoaffinity purification procedure for the isolation of electrophoretically pure proenzyme. By the methodologies described, human procathepsin B can now be obtained in high yield. This should facilitate studies of its interactions with protease inhibitors, other proteases, extracellular matrices, cell-surface proteins and biological substrates that may be of relevance to the pathobiological functions of this enzyme.

Demonstration and characterization of hippocampal cholinergic neurostimulating peptide (HCNP) processing enzyme activity in rat hippocampus

Hippocampal cholinergic neurostimulating peptide (HCNP) stimulates cholinergic activity of cultured medial septal nuclei explants. It consists of eleven amino acids that are located at the N-terminal region of its precursor protein. This report concerns the demonstration and characterization of an HCNP processing enzyme that cleaves the bioactive undecapeptide from the precursor. The enzyme was purified from the hippocampus of young Wistar rats. A synthetic deacetylated peptide (peptide(1-26)) consisting of the N-terminal 26 amino acids of the HCNP precursor protein served as substrate. The product of the enzyme reaction was identified and quantitated by HPLC using deacetylated HCNP as standard. The amount of undecapeptide generated was directly proportional to the time of incubation of the enzyme reaction mixture. From molecular sieving chromatography it was estimated that the molecular mass of the enzyme is close to 68 kDa. The HCNP processing enzyme has a pH optimum of 6.0 and a K m of 0.50 mM for peptide(1-26). Preincubation at 56 degrees C causes rapid inactivation of the HCNP processing activity. Enzyme activity is enhanced by EDTA and 1,4-dithiothreitol, and inhibited by antipain, chymostatin and E-64. These findings suggest that the enzyme probably has a thiol group in its active site. This novel enzyme of the hippocampus may represent a valuable tool for further studies on the general protein metabolism in the central nervous system, as well as for elucidating the neurochemical aspects of neurodegenerative disorders.

Rat epidermal cathepsin B: purification and characterization of proteolytic properties toward filaggrin and synthetic substrates

The aim of this study was to purify epidermal cathepsin B from rat skin and investigate its proteolytic activities on filaggrin and several synthetic substrates. The molecular weight of purified monomeric cathepsin B was estimated to be 30 kDa by SDS-polyacrylamide gel electrophoresis. The amino acid composition, similar to that of liver cathepsin B, indicated the enzyme to be an acidic protease. The enzyme had strong hydrolytic activity toward N-benzyloxy-carbonyl-L-arginyl-L-arginine-7-amido-4-methylcoumarin (Z-Arg-Arg-MCA) (152 mU/mg) and N-benzyloxycarbonyl-L-phenylalanyl-L-arginine-7-amido-4-methylcoumarin (424 mU/mg), but had no proteolytic activity toward L-arginine-7-amido-4-methylcoumarin. The Km value for Z-Arg-Arg MCA was 0.34 mM and pH optimum was 5.5. Cathepsin B degraded rat epidermal filaggrin into small fragments at pH 4.0 and 5.5., and was inhibited by a specific cysteine proteinase inhibitor, N-[N-(L-3-trans-carboxyoxirane-2-carbonyl)L-leucyl]- agmatin. This study demonstrated that filaggrin was susceptible to degradation by cathepsin B. Such an action may have relevance to skin differentiation in which acid proteases are thought to participate.

Muscle fiber degradation in distal myopathy with rimmed vacuoles

Late-onset distal myopathy showed numerous rimmed vacuoles with the same properties as autophagic vacuoles. Electron microscopy showed numerous degenerated mitochondria, glycogen, or cell membranes in rimmed vacuoles, but no evidence that these vacuoles engulfed and contained intact or partially disrupted myofibrils. Immunostaining for myosin, alpha-actinin, and actin, however, was sometimes positive within the vacuoles. Compared to the control muscle, there was increased staining activity by calpain around the rimmed vacuoles or in the cytoplasm of mainly atrophic fibers. The result seems to indicate an increase of calpain activity in these muscle fibers. We hypothesize that the myofibrils as well as mitochondria, glycogen, or cell membranes in this myopathy are degraded finally through a lysosomal autophagic process. However, the breakdown of the myofibrils may be not initiated by lysosomal activation; rather it may be the result of extralysosomal processes such as the calpain system.

Abnormal distribution of cathepsin proteinases and endogenous inhibitors (cystatins) in the hippocampus of patients with Alzheimer's disease, parkinsonism-dementia complex on Guam, and senile dementia and in the aged

The immunolocalization of cathepsins B(CB), H and L and cystatins alpha(C alpha) and beta(C beta) were examined in the hippocampus of cases of sporadic Alzheimer's disease (12 cases), parkinsonism-dementia complex on Guam (eight cases), senile dementia of Alzheimer type (two cases), aged subjects with marked senile change (one case) and controls (12 cases, including six normal subjects). CB was lower in most nerve cells in patients than in controls, but markedly increased at the sites of intracellular neurofibrillary tangles (NFTs) and degenerative neurites and/or dendrites in and outside senile plaques (SPs), indicating its close involvement in the metabolisms of various proteins in NFT and SPs. Abundant C alpha and C beta were demonstrated in SP amyloid, suggesting that they are amyloid constituents or co-exist with amyloid. The present study indicated that CB, C alpha and C beta are closely involved in abnormal protein metabolism in NFTs and SP amyloid and suggested that degeneration or denaturation of intracellular proteins, including substrates for proteases and lysosomes, from some acquired cause, results in absolute and/or relative overload for these proteolytic systems, including their inhibitors. This results in incomplete and/or abnormal proteolysis related to NFT and/or amyloid formation.

Inhibition by acidic phospholipids of protein degradation by ER-60 protease, a novel cysteine protease, of endoplasmic reticulum

A protein (ER60) with sequence similarity to phosphoinositide-specific phospholipase C-alpha purified from rat liver endoplasmic reticulum (ER) degraded ER resident proteins and is really a protease [(1992) J. Biol. Chem. 265, 15152-15159]. Therefore, ER60 is called ER-60 protease. We now show that negatively charged phospholipids, phosphatidylinositol, phosphatidylinositol 4,5-bisphosphate and phosphatidylserine inhibit ER protein degradation by ER-60 protease. Phosphatidylcholine and phosphatidylethanolamine show no effect on the activity of ER-60 protease. With the use of protease inhibitors, ER-60 protease is shown to be a novel cysteine protease distinct from those of the cytosol and lysosomes.

Human tumour cathepsin B. Comparison with normal liver cathepsin B

Cathepsin B was purified from normal human liver and several human tumour tissues and partially characterized. Three forms of cathepsin B, with molecular masses of 25 kDa, 26 kDa (the two appearing as a doublet) and 30 kDa, were detected in SDS/polyacrylamide gels. The 25-26 kDa doublet was associated with the fractions from tumours and normal liver containing the highest cathepsin B activity. Cathepsin B from both sources showed similar pH optima. Both normal liver and tumour cathepsin B exhibited similar kinetics against selected synthetic substrates. At neutral pH and 24 degrees C, cathepsin B from both normal liver and tumour exhibited a lower Km and a higher kcat./Km than at pH 6.0. Their inhibitory profiles against synthetic inhibitors were also similar. Immunological studies with a monospecific antibody against the mature double-chain form of human liver cathepsin B and an antibody against a cathepsin B-derived synthetic peptide established the immunological similarity of liver and tumour enzymes. The N-terminal sequences of the 25 kDa and 26 kDa forms were identical with that of the heavy chain of the mature double-chain form of human cathepsin B, whereas the N-terminal sequence of the 30 kDa species was identical with that of the single-chain form of human cathepsin B. Treatment of the double-chain form of cathepsin B from normal liver and tumours with the endoglycosidase peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase converted the 26 kDa form into 25 kDa in SDS/polyacrylamide gels, suggesting that cathepsin B may exist as both glycosylated and unglycosylated forms. Our results, in contrast with those reported earlier for mouse cathepsin B, indicate that human liver and tumour cathepsin B are similar.

Purification and characterization of cathepsin H from hepatopancreas of carp Cyprinus carpio

1. Cathepsin H was purified about 5400-fold from hepatopancreas of carp (Cyprinus carpio) by the method involving ammonium sulfate fractionation, and chromatography on S-Sepharose, DEAE-Sephacel, Ultrogel AcA54, Concanavalin A-Sepharose 4B and GPC on Protein-Pak 125. 2. The purified cathepsin H gave a single protein band on analytical-PAGE, but migrated as two bands of 27,000 and 23,000 mol. wt on SDS-PAGE. 3. Cathepsin H had a pH and temperature optimum of 6.5 and 45 degrees C using Arg-MCA as a substrate, respectively, and was activated by sulfhydryl compounds and inhibited by cysteine protease inhibitors and metal compounds having high reactivities at cysteine residue. 4. The carp hepatopancreas cathepsin H immunoreacted with the monospecific antibody against rat liver cathepsin H, and did not react with the antibodies against carp hepatopancreas cathepsins B and L by the method of immunoelectrophoretic blotting.

Cystatin activity in gingival crevicular fluid from periodontal disease patients measured by a new quantitative analysis method

Cystatins are protein inhibitors of cysteine proteinases, which are believed to play an important role in the pathogenesis of periodontal disease. In this study, we report a new sensitive method for the quantitative analysis of cystatin activity in a small amount of crude sample such as gingival crevicular fluid. Cystatin activity in the crude sample was determined by using active site-titrated papain, which is a cysteine proteinase from the plant Carica papaya. Crude samples usually contain endogenous cysteine proteinases. These competed with the added papain for the active sites of the cystatins. The cystatin-cysteine proteinase complex was able to be dissociated by the addition of papain. This competition and dissociation could interfere with the determination of cystatin activity, since some of the cysteine proteinases, such as cathepsin B, hydrolyzed the specific substrate for papain during titration with the papain. In order to exclude this interference and measure total cystatin activity, the crude sample must be alkalinized (pH 11.0) for 5 min at 4 degrees C followed by 10 min at 40 degrees C before titration with papain. The minimum detectable amount of cystatins was 20 fmol/assay when it was calculated per mole of papain inhibitory sites. Using this method, significant levels of cystatin activity were detected in all the samples of gingival crevicular fluid taken from periodontal disease patients. These results suggest that cystatins could regulate the cysteine proteinases in gingival crevicular fluid and that this new method could be useful to clarify the role of cystatins in the pathogenesis of periodontal disease.

Degradation of extracellular-matrix proteins by human cathepsin B from normal and tumour tissues

Our laboratory has previously demonstrated that increased malignancy of several histological types of human and animal tumours is associated with increases in their cathepsin B activity, particularly cathepsin B activity associated with plasma-membrane/endosomal vesicles or shed vesicles. Here we report that cathepsin B from normal or tumour tissues degrades purified extracellular-matrix components, type IV collagen, laminin and fibronectin, at both acid pH and neutral pH. The number and sizes of degradation products were analysed by SDS/PAGE. Cathepsin B from both sources exhibited similar activities towards, and similar patterns of cleavage of, the extracellular-matrix proteins. At neutral pH, cathepsin B from both sources appeared to undergo autodegradation, a process that was decreased in the presence of alternative substrates such as the extracellular-matrix proteins. Cathepsin B readily degraded type IV collagen at 25 degrees C, indicating activity towards native type IV collagen. Fibronectin degradation products of 100-200 kDa and of 18 and 22 kDa were observed. A single 70 kDa fragment was released from laminin under non-reducing conditions and multiple fragments ranging from 45 to 200 kDa under reducing conditions. These results suggest that cathepsin B at or near the surface of malignant tumour cells may play a functional role in the focal dissolution of extracellular matrices.

A low-molecular-mass Kazal-type protease inhibitor isolated from rat hepatocytes is identical to rat pancreatic secretory trypsin inhibitor II. Purification and amino acid sequence

A low-molecular-mass serine protease inhibitor was purified from hepatocytes and liver of rats. It was found to be a single polypeptide of 56 amino acid residues corresponding to Mr = 6224, a value that is in agreement with the molecular mass determined by gel chromatography. The inhibitor formed a complex in a molar ratio of 1:1 with trypsin. Its complete amino acid sequence was identical with that of pancreatic secretory trypsin inhibitor II (PSTI-II) in pancreatic juice, but not with that of PSTI-I [Uda, K., Ogawa, M., Shibata, T., Murata, A., Mori, T., Kikuchi, N., Yoshida, N., Tsunasawa, S. & Sakiyama, F. (1988) Biol. Chem. Hoppe-Seyler 369, 55-61]. PSTIs have been reported to be primarily pancreatic secretory products, but in have been reported to be primarily pancreatic secretory products, but in patients immunoreactive PSTI was found in the plasma and urine during acute inflammatory disease and shown to be produced ectopically in cancer tissues. Here we report for the first time that PSTI-II is present in other normal tissues besides the pancreas.

Protease-specificity of Kunitz inhibitor domain of Alzheimer's disease amyloid protein precursor

The putative inhibitor domain of Alzheimer's disease amyloid protein precursor was purified from E. coli containing a synthetic gene encoding the Kunitz domain. The purified protein (A4 inhibitor) inhibited the activity of trypsin, forming a 1:1 molar complex with the enzyme. It also strongly inhibited plasmin (Ki = 7.5 x 10(-11) M) from human serum and tryptase (Ki = 2.2 x 10(-10) M) from rat mast cells (tryptase M). In addition, it inhibited rat pancreatic trypsin, alpha-chymotrypsin and kallikrein and human serum kallikrein, but did not inhibit rat chymase, pancreatic elastase, alpha-thrombin, urokinase, papain or cathepsin B.

Variations in immunoreactivity of angiotensinogen and cathepsins B and H in rat hepatocytes over 24 hours

To examine variations in immunoreactivity of angiotensinogen and cathepsins B and H in hepatocytes over 24 hr, rat liver was examined immunohistochemically. Immunoreactivity of angiotensinogen and cathepsins B and H in periportal and perivenous hepatocytes varied significantly over 24 hr, when analyzed by an image analyzer. In periportal and perivenous hepatocytes, immunoreactivity of angiotensinogen was highest at 0800 hr and lowest at 2000 hr or 0000 hr, whereas that of cathepsins B and H was maximal at 1600 hr and minimal at 0400 hr or 0800 hr. Proteolytic activities of cathepsins B and H in liver extracts varied in parallel to the variations in immunoreactivity of these enzymes. Localization of angiotensinogen in the liver acinus was inversely correlated to that of cathepsins B and H; angiotensinogen was predominantly localized in periportal hepatocytes, but cathepsins B and H were in perivenous hepatocytes at each time point examined. These results suggest that angiotensinogen in hepatocytes is actively synthesized and secreted early in the light period, whereas proteolytic activities in lysosomes of hepatocytes are augmented late in the light period.

Inhibitory effect of di- and tripeptidyl aldehydes on calpains and cathepsins

Eight different di- and tripeptidyl aldehyde derivatives, each having at its C-terminus an aldehyde analog of L-norleucine, L-methionine, or L-phenylalanine with a preceding L-leucine residue, were synthesized and tested for their inhibitory effects on several serine and cysteine endopeptidases. These compounds showed almost no inhibition of trypsin, and only weak inhibition of alpha-chymotrypsin and cathepsin H, while they exhibited marked inhibition of cathepsin B less than calpain II congruent to calpain I less than cathepsin L, being stronger in this order. The mode of inhibition of these cysteine proteinases was competitive for the peptide substrate used and inhibitor constants (Ki) were calculated from the Dixon plot. The best inhibitors found were: 4-phenyl-butyryl-Leu-Met-H for calpain I (Ki, 36 nM) and calpain II (Ki, 50 nM); acetyl-Leu-Leu-nLeu-H for cathepsin L (Ki, 0.5 nM); acetyl-Leu-Leu-Met-H for cathepsin B (Ki, 100 nM).

Purification and characterization of a protease from Xenopus embryos

A proteolytic enzyme was purified from Xenopus embryos. The purification procedure consisted of fractionation of an extract of embryos with acetone, gel filtration of Sephadex G-75 and chromatography on carboxymethyl-cellulose and hydroxylapatite. The preparation of enzyme appeared to be homogeneous as judged by electrophoresis in polyacrylamide gels. This protease had a molecular mass of 43-44 kDa and was composed of two subunits with molecular masses of 30 kDa and 13 kDa. The optimal pH of the reaction catalysed by the protease was approximately 4.0. This proteolytic activity was inhibited by antipain, leupeptin and iodoacetic acid; it was not affected by phenylmethylsulfonyl fluoride and pepstatin; and it was enhanced by dithiothreitol. In the presence of RNA, the optimal pH was shifted from pH 4.0 to pH 4.5. The protease was activated by addition of total RNA from Xenopus embryos, by poly(rU) or poly(rG). In contrast, after addition of tRNA or poly(rC), no activation of the protease was observed.

Acid-stable trypsin-plasmin inhibitors formed enzymatically from plasma precursor protein

Enzymatic formation of acid-stable trypsin-plasmin inhibitors (ASTPIs) in human plasma with several proteinases, particularly SH-proteinases, was demonstrated. The maximal activity obtained with bromelain was 40 U/ml plasma, which corresponded to about a 10-fold increase as compared to the untreated control plasma (4.2 U/ml). Gel filtration revealed at least two ASTPI activity peaks of molecular weight 16,000 (main peak) and 8000 (minor peak). The main ASTPI was further purified by trypsin-Sepharose affinity chromatography, isoelectric focusing and gel filtration on Sephadex G-75 superfine. The purified inhibitor was found to be identical to the active fragment of plasma ASTPI or urinary trypsin inhibitor (UTI) formed by bromelain treatment. It had an isoelectric point (pI) of 3.7, a molecular weight of 16,000 by SDS-polyacrylamide gel electrophoresis and was a glycine- and glutamic acid-rich protein lacking histidine. The NH2-terminal amino acid sequence was H2N-(Lys)-Glu-Asp-Ser-X-Gln-Leu-Gly-Tyr-Ser-Ala-Gly-Pro-X-Met-Gly-Met-Th r-X-Arg - Tyr-Phe-Tyr-... COOH, which was homologous to the Lys22-Met36 part (or Glu23-Met36 part; 30% of the total) of the plasma ASTPI or UTI molecule (molecular weight 70,000-80,000 by gel filtration). The purified ASTPI displayed the same antigenicity as UTI and exerted strong inhibitory effects on trypsin, chymotrypsin and plasmin amidolysis, but had a much lesser effect on plasmin fibrinolysis. It also strongly inhibited non-plasmic fibrinolysis with human leukocyte proteinase and earthworm proteinase.

Biosynthesis of lysosomal cathepsins B and H in cultured rat hepatocytes

The biosynthesis of lysosomal cysteine proteases, cathepsins B and H, was investigated by using pulse-chase experiments in vivo in primary cultures of rat hepatocytes. Cathepsins B and H were isolated from either total cell extracts or culture medium labeled with [35S]methionine by immunoprecipitation and analyzed for their molecular forms. Within 60 min of chase, cellular proforms of cathepsins B of 39 kDa and H of 41 kDa were converted to single-chain form cathepsins B of 29 kDa and H of 28 kDa, respectively, and persisted as these forms even after 12-h chase periods. The proforms of cathepsins B and H derived from pulse-labeling experiments showed complete susceptibility to endoglycosidase H treatment, indicating that these proenzymes bear high-mannose-type oligosaccharides at the stage of initial events of biosynthesis. In the presence of tunicamycin, unglycosylated proenzymes of cathepsins B of 35 kDa and H of 34 kDa were found to be secreted into the extracellular medium without undergoing proteolytic processing. Furthermore, in the presence of swainsonine, a potent inhibitor of Golgi mannosidase II, considerable amounts of the proenzymes were secreted and accumulated in the medium during chasing periods. These results suggest that the oligosaccharide moiety of these enzymes would be necessary for the intracellular sorting mechanism. In monensin-treated cells, the conversion of intracellular proenzymes to mature enzymes was significantly inhibited and the proenzymes were secreted into the medium. In the presence of chloroquine or ammonium chloride, proteolytic processing of the proenzymes was completely prevented and the enhanced secretion of proenzymes was observed. These results suggest that in the presence of lysosomotropic amines the intracellular sorting of proenzymes might not occur properly during biosynthesis.

Inhibition of cathepsin L-induced degradation of epidermal growth factor receptors by c-Ha-ras gene products

The inhibitory activities of c-Ha-ras gene products (p21s) toward several cysteine proteinases have been investigated. The activity of cathepsin L was inhibited by p21s most effectively while those of cathepsin B and papain were slightly inhibited by p21s. p21s did not show any inhibitory activity toward cathepsin H. In order to connect the protease-inhibitor activity of p21s with cell growth, the degradation of epidermal growth factor receptors (EGF-receptors) was investigated. EGF-receptors were preferentially cleaved by cathepsin L but not by cathepsin B or H. The cleavage of EGF-receptors by cathepsin L was inhibited by p21s dose-dependently. These results raise the possibility that p21s can suppress the degradation of growth-related proteins such as EGF-receptors and thereby affect cell growth.

Identification of latent procathepsins B and L in microsomal lumen: characterization of enzymatic activation and proteolytic processing in vitro

Procathepsins B and L in the hepatic endoplasmic lumen were identified as having a molecular weight of 39,000 by immunoblot analysis. The proenzymes were then purified to remove the mature enzymes by concanavalin A-Sepharose chromatography. The concanavalin A-adsorbed fractions containing the proenzymes showed no appreciable activities of cathepsins B and L. When those fractions were incubated at pH 3.0, the enzymatic activities markedly increased: the activities of cathepsins B and L after 36 h incubation were 60 and 210 times those of the controls, respectively. Immunoblot analysis showed that after 36 h incubation the proenzymes disappeared and the mature enzymes increased. Thus the proenzymes were processed to the mature enzymes under acidic conditions of pH 3.0. The marked increases of enzymatic activities and the conversion of the proenzymes to the mature forms were completely blocked with pepstatin, which is a potent inhibitor of aspartic proteases. The results strongly suggested that a processing protease for procathepsins B and L might be cathepsin D, a major lysosomal aspartic protease. Indeed, lysosomal cathepsin D could convert microsomal procathepsin B to the mature enzyme in vitro. Therefore, procathepsins B and L seem first to be synthesized as enzymatically inactive forms in endoplasmic reticulum and successively may be converted into active forms by cathepsin D in lysosomal compartments.

Immunolocalization of cathepsins B, H and L in skeletal muscle of X-linked muscular dystrophy (mdx) mouse

The amounts of non-collagen proteins (muscle structural proteins) and the activity of creatine kinase were significantly decreased in muscles of 28-day-old mdx mice. The activities of lysosomal thiol proteases such as cathepsins B and L were increased in muscles of mdx mice at as early as 10 days of age. Endogenous thiol proteinase inhibitor and various lysosomal hydrolases also showed increased activities. The localization of cathepsins B, H and L, and endogenous thiol proteinase inhibitor was investigated using the respective specific antibodies. While only invading macrophages were stained strongly with anticathepsin B and H, and anti-thiol proteinase inhibitor antibodies, cathepsin L was localized in muscle cells as well as in invading macrophages. Cathepsin L in muscle cells itself may initially degrade muscle structural proteins, before lysosomal thiol proteases, mainly derived from macrophages, degrade them in skeletal muscles of mdx mice.

Monoclonal antibody toward lysosomal cathepsin B cross-reacts preferentially with distinct histone classes

1. A set of monoclonal antibodies (Mab) was prepared against cathepsin B (CB) from rat preputial-gland, an organ characterized by rapidly-renewing cell populations, which is a uniquely enriched source of lysosomal enzymes, including CB. Minute amounts of CB are known to be transferred abruptly to the nuclear compartment in a variety of activated cells. 2. Since, on the basis of its stringent substrate requirements, CB was expected to function at limited protein loci in chromatin, Mab Line II-B4 was used to probe Western blots of chromatin fractions and selected proteins. 3. The Mab, which was not directed against the active site of CB, cross-reacted preferentially with histones 3 and 4 (H3 and H4) in acid-soluble fractions of chromatin from rat preputial-gland. Line II-B4 also recognized H3 and H4 selectively in calf thymus histones and among histones purified from a wide range of sources from yeast to man. HMG 1 was minimally immunoreactive among preputial gland constituents and carbonic anhydrase (CA) was also sensitive to the Mab. 4. The common determinants were not shared by any of the H1 series, nor by H2A, H2B, protein A24 or a wide range of natural and synthetic products. 5. Origin of the antigenicity was traced by chemical modifications of H3, H4 and CA to the critical contribution of arginine and hydrophobic amino acid residues in its immediate environment, indicating that Line II-B4 may be directed against an epitope comprising the specific binding-site of CB and its selective substrate(s). 6. These data suggest that certain highly conserved cellular constituents may be uniquely vulnerable to limited proteolysis in preproliferative cells responding to mitotic signals.

Intracellular transport and processing of lysosomal cathepsin B

Intracellular transport and processing of lysosomal cathepsin B was investigated in the subcellular fractions of rat liver by pulse-labeling experiments with [35S]methionine in vivo. A newly synthesized procathepsin B with a molecular weight of 39 kDa firstly appeared in the rough microsomal fraction at 10 min postinjection of label. This procathepsin B moved from the microsomal fractions to the Golgi subfractions at 30 min postinjection, and then a processed mature enzyme appeared in the lysosomal fraction at 60 min. These results suggest that the propeptide-processing of procathepsin B takes place in lysosomes in the course of intracellular transport from endoplasmic reticulum through Golgi complex to lysosomes.

Autodegradation of lysosomal cysteine proteinases

Repeated injections of Ep-475, a potent cysteine proteinase inhibitor, into rats caused several-fold increase in the hepatic contents of the lysosomal cysteine proteinases cathepsin B, H and L and in the activities of other lysosomal hydrolases. The rates of degradation of these lysosomal enzymes, estimated by repeated injections of cycloheximide, were found to be retarded in Ep475-treated rats, indicating that lysosomal cysteine proteinases are involved in degradation of lysosomal enzymes including proteinases.

Human and bovine brain cathepsin L and cathepsin H: purification, physico-chemical properties, and specificity

Cathespin L (EC 3.4.22.15) and cathepsin H (EC 3.4.22.16) have been purified from brain cortex to apparent homogeneity by a simultaneous procedure involving acid extraction of homogenate at pH 4.2, ammonium sulfate fractionation (30-80%), chromatography on pepstatin-Sepharose, CM-Sephadex C-50, DEAE-Sephadex A-50, phenyl- and concanavalin A-Sepharose and isoelectric focusing. Cathepsin L and cathepsin H were assayed in the presence of dithiothreitol and Na2EDTA (2 mM each) with Z-Phe-Arg-NHMec (pH 5.5) and Lys-NNa (pH 6.5) respectively. Cathepsin L consists of 2 polypeptide chains with Mr 25,000 and 5,000, Mr of cathepsin H is 28,000. Cathepsin L exists in brain tissue in two multiple forms with pI values 5.7 and 5.9, pI of cathepsin H is 6.8. Substrate specificity of these thiol proteinases was tested with proteins (pyridoxyl-hemoglobin, azocasein) and low Mr naphthylamide and methylcoumarylamide substrates: Lys-NNa, Arg-NNa, Dz-Arg-NNa, Z-Arg-Arg-NNaOMe, Z-Phe-Arg-NHMec, Z-Phe, Val-Arg-NHMec, Z-Gly-Gly-Arg-NHMec. Z-Phe-Arg-NHMec is the best substrate for cathepsin L (KM = 5 microM, Kcat = 21 s-1), Arg-NNa--for cathepsin H (KM = 0.1 mM, Kcat = 1.93 s-1), being endoaminopeptidase cathepsin H also hydrolyses Bz-Arg-NNa (KM = 0.7 mM, Kcat = 1.3 s-1). Both proteinases are inhibited by traditional inhibitors of cysteine proteinases and E-64, but leupeptin turned to be more effective inhibitor of cathepsin L (Ki = 2.4 nM) than of cathepsin H (Ki = 9.2 microM), the latter enzyme being sensitive to puromycin and benzethonium chloride as well.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation and characterization of cathepsin B from bovine brain

Cathepsin B (EC 3.4.22.1) was purified 746-fold with a 21% recovery from bovine brain by autolysis, fractional precipitation with acetone, carboxy-methyl-Sephadex chromatography, affinity chromatography on a cystamine containing column and gel filtration chromatography. The purified cathepsin B eluted on gel filtration with an apparent molecular weight of 27,000 but was resolved into three bands of 30,000, 25,000 and 5,000 molecular weight by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE). Antibodies to cathepsin B, raised against the 30,000 dalton band, were shown by immunoblots to react with both the 30,000 and 25,000 dalton proteins with results suggesting that the former predominated as the immunoreactive form in bovine brain homogenates. Isoelectric focusing demonstrated multiple bands, ranging from pH 4.75-5.2 with the major band at pH 5.1-5.2, all of which were capable of degrading N alpha-carbobenzoxy-L-arginyl-L-arginine 4-methoxy-beta-naphthylamide. The cathepsin B activity against N alpha-benzoyl-DL-arginine beta-naphthylamide (BANA) and bovine myelin basic protein (MBP) had a pH optimum of pH 6.0. The Km for the degradation of BANA was 1.0 mM and 5.1 mM when assayed in the presence of 1% and 2.5% dimethylsulfoxide, respectively. Cathepsin B from bovine brain has many properties similar to cathepsin B isolated from other organs. The degradative effect of cathepsin B on MBP suggests a role for this proteinase in inflammatory demyelination.

Purification and properties of a thiol protease from lung fluke adult Paragonimus ohirai

The thiol protease was purified from adult Paragonimus ohirai by alpha 1-antitrypsin-Sepharose, Sephadex G-75 and CM-cellulose, measuring its activities to hydrolyze hemoglobin and tosyl-L-lysine alpha-naphthyl-ester. The purified protease showed a single band on polyacrylamide disc gel isoelectrophoresis as zymogram with Tos-Lys-NE and also by protein staining, and its pI was found to be 6.4. The molecular weight was calculated to be 29,000 by gel filtration and 27,000 by SDS-polyacrylamide gel electrophoresis as a single polypeptide. The protease hydrolyzed hemoglobin and Tos-Lys-NE optimally at pH 4.0 and 5.0, respectively. The both hydrolyzing activities were inhibited by alpha 1-AT and soybean trypsin inhibitor as well as thiol protease inhibitors such as antipain, E-64 and p-hydroxymercuriphenylsulfonate. These results indicate that this enzyme is a new type thiol protease.

A new function of kininogens as thiol-proteinase inhibitors: inhibition of papain and cathepsins B, H and L by bovine, rat and human plasma kininogens

The amidolytic activities of papain and rat liver cathepsins B, H and L were strongly inhibited by high (HMM) and low (LMM) molecular mass kininogens from bovine, human and rat plasmas, and their Ki values were estimated to be in the order of 10(-10) - 10(-11)M for papain and 10(-8) - 10(-9)M for cathepsins. The derivatives of bovine kininogens, HMM kinin-free protein, HMM kinin- and fragment 1 X 2-free protein, and LMM kinin-free protein also showed strong inhibitory activity toward these thiol-proteinases. These results suggest that a reactive site which interacts with thiol-proteinases is contained in the heavy chain portion in kininogens.

Amino acid sequence of human liver cathepsin B

The complete amino acid sequence of cathepsin B (EC 3.4.22.1) from human liver was determined. The 252-residue sequence was obtained by automated solid-phase Edman degradation of the light and heavy chain resulting from limited proteolysis of the single-chain enzyme and of fragments produced by cyanogen bromide and enzymatic cleavage of the heavy chain. Human liver cathepsin B has 83.7% identical residues with the corresponding enzyme from rat liver. Comparison of both mammalian cathepsin B sequences with the sequence of papain provides further evidence that lysosomal and plant cysteine proteinases have evolved from a common ancestor and share a similar catalytic mechanism.