Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.24.11 (CD10)
 9,792 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Cathepsin H is an endoaminopeptidase belonging to the group of thiol enzymes. It was purified from rat liver lysosomes by gel filtration on Sephadex G-75, chromatography on CM-Sephadex C-50, on DEAE-Cellulose DE-52 and subsequently on an organomercurial absorbent. 2. The molecular weight of cathepsin H was found to be 28,000 and the isoelectric point was estimated to be at pH 7.1 by analytical isoelectric focusing. 3. Cathepsin H has to be designated as endoaminopeptidase, because it catalyzes the hydrolysis of proteins, N-terminal substituted proteins and amino acid derivatives, respectively, as well as of peptides of various chain length and N-terminal free amino acid derivatives. Cathepsin H shows amidase and esterase activity, but it does not show carboxypeptidase activity. The finding of the amino- and endopeptidase nature of cathepsin H has been revealed mainly by the results obtained with inhibitors and by the rather high temperature stability of the enzyme. The chlormethyl ketone of leucine proves to be the strongest inhibitor of the aminopeptidase as well as of the endopeptidase activity, whereas leupeptin endopeptidase activity and endopeptidase substrates inhibit competitively the aminopeptidase activity. 5. Cathepsin H shows highest activity at pH 6.0 in the presence of 1--5 mM GSH and EDTA. 6. The enzyme is stable for several months at slightly acid pH values in a deep frozen state.
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PMID:Cathepsin H: an endoaminopeptidase from rat liver lysosomes. 90 30

Employing soluble denatured protein substrates and their derivatives, the proteolytic activity of rat cathepsin H was investigated. The enzyme showed aminopeptidase activity which sequentially released amino acid from the N-terminal of the substrate. The aminopeptidase activity did not act on N alpha-acetylated peptides and showed moderate ionic-strength dependence when methionyl-methylcoumarylamide was employed as a substrate. These results indicate that the activity essentially requires an N-terminal free amino group of the substrate and recognizes it electrostatically to some extent. On the other hand, the enzyme was also indicated to exhibit endopeptidase activity by employing appropriate N alpha-acetylated peptide substrates. In contrast to the aminopeptidase activity, the endopeptidase activity showed rather strict specificity, preferring hydrophobic residues at P2 and P3 sites. Because of the broad specificity and high efficiency of the aminopeptidase activity, it was difficult to directly observe endopeptidase activity in the digestion of large peptide substrates with a free alpha-amino terminal. Thus, this is the first experimental evidence that indicates endopeptidase activity by assigning internal peptide bonds cleaved by this activity. From this data, we proposed a model of the binding site of this enzyme.
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PMID:Endo- and aminopeptidase activities of rat cathepsin H. 152 52

Proteins sequestered by a non-selective bulk process within the lysosomes turn over with an apparent half-life of about 8 minutes and this rapid lysosomal proteolysis is initiated by endopeptidases, in particular by the cathepsins D and L. We describe also the cathepsins B and H which show mainly exopeptidase and only low endopeptidase activity. Especially cathepsin H is most probably the only lysosomal aminopeptidase in many cell types. Additionally, the properties of other mammalian lysosomal endo- and exopeptidases are compared. Finally, we discuss some of the conditions for the action of lysosomal proteases as the low intralysosomal pH, the high part of lysosomal thiol groups and the absence of intralysosomal proteinase inhibitors.
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PMID:Proteases and proteolysis in the lysosome. 174 Jan 87

Cathepsin H purified from porcine spleens was studied for its specificity against various peptide and denatured protein substrates. The enzyme degraded all peptide substrates exclusively by an aminopeptidase activity. The enzyme preferentially released NH2-terminal amino acid residues with large hydrophobic (Phe, Trp, Leu, and Tyr) or basic (Arg and Lys) side chains. Amino acids containing small or polar side chains were not released. Peptides with a proline in the NH2-terminal or penultimate positions were not hydrolyzed either. Large polypeptides such as reduced and carboxymethylated soybean trypsin inhibitor and aldolase were not degraded. These results indicate that cathepsin H is an exopeptidase but not an endopeptidase. We propose that the biological role of this enzyme is the degradation of tissue proteins in lysosomes by its aminopeptidase activity.
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PMID:Porcine spleen cathepsin H hydrolyzes oligopeptides solely by aminopeptidase activity. 339 49

The number of possible subsites of the rat liver cysteine proteinases cathepsin B and cathepsin H was determined in the N-terminal direction from the scissile bond. An elongation of the substrate peptide chain of up to four amino acid residues enhances the hydrolysis rate of both cathepsins. The greatest increase in activity was observed by elongation to the dipeptide substrate for cathepsin B and to the tetrapeptide substrate for cathepsin H. Both proteinases discriminate proline from their subsites S1 and S2, but accept it well in S3. A quantitative distinction between the endopeptidase and the peptidyl dipeptidase activity of cathepsin B was feasible by using two model peptides: (Formula: see text) (Z = benzyloxycarbonyl; X = NH2 or OH; the arrow shows the cleavage site). Whereas the peptide acid, representing the peptidyl dipeptidase substrate, was hydrolysed by cathepsin B twice as fast as the peptide amide as an endopeptidase substrate, cathepsin H clearly had a preference for the amide substrate.
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PMID:Enzyme-substrate interactions in the hydrolysis of peptides by cathepsins B and H from rat liver. 366 63

The action of two earlier isolated highly purified spleen thiol proteinases on angiotensins I and II, bradykinin and kallidin was investigated. It was demonstrated that proteinase I which is apparently cathepsin L from bovine spleen brings about rapid inactivation of angiotensin II with a splitting of the Tyr-Ile bond and a formation of two tetrapeptides. Proteinases I also split angiotensin I. Proteinase I partially inactivates bradykinin and kallidin by splitting the Gly4-Phe5 bond. The activity of proteinase I toward angiotensin II is about 50 times higher than that toward bradykinin. The corresponding values of Km and V are 7.5 X 10(-5) M and 10.0 mumole/min/mg. The possible role of proteinase I in angiotensin II inactivation under physiological conditions is discussed. Proteinase II converts kallidin to bradykinin by splitting off the N-terminal lysine. Proteinase II causes partial inactivation of bradykinin by splitting of the Gly4-Phe5 and Phe5-Ser6 bonds of this peptide. Proteinase II possesses both aminopeptidase and endopeptidase activities and is therefore cathepsin H from spleen. Proteinase II does not split either angiotensin I or angiotensin II.
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PMID:[Action of two thiol proteinases from the spleen which are active in neutral media on vasoactive peptides]. 634 1

The mature bovine cathepsin C (CC) molecule is composed of four identical monomers, each proteolytically processed into three chains. Five intrachain disulfides and three nonpaired cysteine residues per monomer were identified. Beside catalytic Cys234 in the active site, free-thiol Cys331 and Cys424 were characterized. Cys424 can be classified as inaccessible buried residue. Selective modification of Cys331 results in dissociation of native CC tetramer into dimers. The 3D homology-based model of the CC catalytic core suggests that Cys331 becomes exposed as the activation peptide is removed during procathepsin C activation. The model further shows that exposed Cys331 is surrounded by a surface hydrophobic cluster, unique to CC, forming a dimer-dimer interaction interface. Substrate/inhibitor recognition of the active site in the CC dimer differs significantly from that in the native tetramer. Taken together, a mechanism is proposed that assumes that the CC tetramer formation results in a site-specific occlusion of endopeptidase-like active site cleft of each CC monomeric unit. Thus, tetramerization provides for the structural basis of the dipeptidyl peptidase activity of CC through a substrate access-limiting mechanism different from those found in homologous monomeric exopeptidases cathepsin H and B. In conclusion, the mechanism of tetramer formation as well as specific posttranslational processing segregates CC in the family of papain proteases.
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PMID:Free-thiol Cys331 exposed during activation process is critical for native tetramer structure of cathepsin C (dipeptidyl peptidase I). 1191 36

The mini-chain of human cathepsin H has been identified as the major structural element determining the protease's substrate specificity. A genetically engineered mutant of human cathepsin H lacking the mini-chain, des[Glu(-18)-Thr(-11)]-cathepsin H, exhibits endopeptidase activity towards the synthetic substrate Z-Phe-Arg-NH-Mec (kcat = 0.4 s(-1), Km = 92 microM, kcat/Km = 4348 M(-1) s(-1)) which is not cleaved by r-wt cathepsin H. However, the mutant enzyme shows only minimal aminopeptidase activity for H-Arg-NH-Mec (kcat = 0.8 s(-1), Km = 3.6 mM, kcat/Km = 222 M(-1) s(-1)) which is one of the best known substrates for native human cathepsin H (kcat = 2.5 s(-1), Km = 150 microM, kcat/Km = 16666 M(-1) s(-1)). Inhibition studies with chicken egg white cystatin and E-64 suggest that the mini-chain normally restricts access of inhibitors to the active site. The kinetic data on substrates hydrolysis and enzyme inhibition point out the role of the mini-chain as a structural framework for transition state stabilization of free alpha-amino groups of substrates and as a structural barrier for endopeptidase-like substrate cleavage.
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PMID:Human cathepsin H: deletion of the mini-chain switches substrate specificity from aminopeptidase to endopeptidase. 1451 96

Human procathepsin H was expressed in the form of inclusion bodies in Escherichia coli. Following refolding and autocatalytic activation, a recombinant cathepsin H form lacking the mini chain was produced. Removal of the mini chain completely abolished aminopeptidase activity of the enzyme and largely increased its endopeptidase activity (approximately 40-fold). Similarly to cathepsin S, Bz-FVR-AMC (k(cat)/K(m) value of 1070 mM(-1) s(-1)) was found to be the preferred substrate of recombinant cathepsin H. However, substrate inhibition was observed at a higher substrate (Z-FR-AMC, Bz-FVR-AMC) concentration. Endopeptidase activity of recombinant cathepsin H was seen also with the protein substrate insulin beta-chain with the major cleavage site between Glu13-Ala14. Recombinant human cathepsin H was inhibited by chicken cystatin, stefin A, and stefin B with the K(i) values in the range of 0.05-0.1 nM, which is slightly tighter than the inhibition of purified cathepsin H by the same inhibitors. These results thus indicate that the cathepsin H mini chain is essential for the aminopeptidase activity of the enzyme but has only a minor effect on the inhibition by cystatins.
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PMID:Recombinant human cathepsin H lacking the mini chain is an endopeptidase. 1462 98

Highly purified human brain cathepsin H (EC 3.4.22.16) was used to study its involvement in degradation of different brain peptides. Its action was determined to be selective. On Leu-enkephalin, dynorphin (1-6), dynorphin (1-13), alpha-neoendorphin, and Lys-bradykinin, it showed a preferential aminopeptidase activity by cleaving off hydrophobic or basic amino acids. It showed no aminopeptidase activity on bradykinin, which has Pro adjacent to its N-terminal amino acid, on neurotensin with blocked N-terminal amino acid, or on dermorphin with second amino acid D-alanine. After prolonged incubation, cathepsin H acted as an endopeptidase. Dermorphin and dynorphin (1-13) were cleaved at bonds with Phe in the P2 position, while dynorphin (1-6), alpha-neoendorphin, bradykinin and Lys-bradykinin were cleaved at bonds with Gly in the P2 position. Further on, it was shown that human brain cathepsin H activity could be controlled in vivo by cystatin C in its full-length form or its [delta1-10] variant, already known to be co-localized in astrocytes, since the Ki values for the inhibition are in the 10(-10) M range.
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PMID:Human brain cathepsin H as a neuropeptide and bradykinin metabolizing enzyme. 1512 51


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