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)

Catalytic amounts of bovine beta-trypsin, bovine alpha-chymotrypsin and porcine plasmin establish a true thermodynamic equilibrium between virgin (I) (reactive site Lys15-Ala16 peptide bond intact) and modified (I) (this bond hydrolyzed) bovine trypsin/kallikrein inhibitor (Kunitz). The very slow reaction rates for attaining equilibrium are pH-dependent and differ for different enzymes. Optimal rates are for beta-trypsin at pH 3.75, for alpha-chymotrypsin at pH 5.5, and for plasmin at pH 5.0. Under conditions of optimum pH the equilibrium is reached with the highest rate by plasmin. In 10(-5)M inhibitor solutions the equilibrium concentrations of virgin and modified inhibitor are established by plasmin after almost 300 days starting from either pure virgin or pure modified inhibitor. Thus, the hydrolysis constant KHyd = [I]/[I] is determined to be 0.33 at pH 5.0. In spite of many unsuccessful attempts, this demonstrates that the reactive site peptide bond Lys15-Ala16 in the bovine trypsin inhibitor (Kunitz) can be hydrolyzed by catalytic amounts of endopeptidase. It further confirms that the hydrolyzed Lys15-Ala16 peptide bond in modified inhibitor is subject to thermodynamic control resynthesis.
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PMID:Hydrolysis-resynthesis equilibrium of the lysine-15--alanine-16 peptide bond in bovine trypsin inhibitor (Kunitz). 0 70

Preparation of ribosomes using different procedures (treatment of postmitochondrial-postlysosomal supernatant or microsomes with 1% triton in 0.15 or 0.5 M KCl and subsequent sucrose gradient centrifugation; treatment of microsomes with 1.5% deoxycholate/2% triton) results in purified ribosomes which contain an endopeptidase activity detectable by breakdown of ribosomal proteins to trichloroacetic acid soluble split products. The proteolytic activity can be recovered also in the extracted proteins of whole ribosomes. With ribosomes the pH optimum of proteolytic breakdown is at about 7. The inhibition of the activity by leupeptin, DIFP and soya bean trypsin inhibitor suggests a serine type of the proteolytic activity.
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PMID:Presence of an endopeptidase activity in rat liver ribosomes. 61 19

Results obtained from experiments dealing with mammalian, bacterial, phage and mitochondrial protein biosynthesis as well as certain enzymatically performed amino acid replacement studies on Kunitz trypsin inhibitor strongly suggest that protein ligation may be occuring in vivo. Amino acid substitution experiments prove the reversibility of endopeptidase reactions, and protein ligation is the reverse of endopeptidase reaction. These experiments are discussed in detail and the suggestion is made that ligation may also be useful in the repair of certain essential proteins which may become damaged.
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PMID:Is there a protein ligase? 95 37

Endothelin-1 (ET-1) is a potent vasoconstrictor peptide secreted by endothelial cells. We investigated whether polymorphonuclear neutrophils (PMN) were able to destroy this peptide by enzymatic hydrolysis produced either by the membrane-bound endopeptidase 24.11 or by lysosomal proteinases released in the medium by activated cells. Resting and activated PMN were incubated with 125I-labelled ET-1 and the degradation fragments were analyzed by HPLC. A marked degradation of ET-1 was observed only in the presence of the stimulated cells, leading to the generation of seven radiolabelled peaks. Addition of phosphoramidon had no effect on the appearance of these metabolites, while soybean trypsin inhibitor abolished almost completely the degradation of the peptide, suggesting a role of cathepsin G in ET-1 hydrolysis. Among the purified leukocyte enzymes tested, cathepsin G hydrolyzed 125I-labelled ET-1 at the higher rate and gave rise to two radiolabelled peaks already observed in the presence of activated PMN. Incubation of unlabelled ET-1 with purified cathepsin G allowed to identify a major cleavage site corresponding to the His16-Leu17 bond, leading to the formation of inactive [1-16] fragments and the C-terminal pentapeptide. This mechanism of ET-1 inactivation could play a role in acute inflammatory reaction where PMN adhere to the vascular endothelial cells.
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PMID:Enzymatic degradation of endothelin-1 by activated human polymorphonuclear neutrophils. 147 5

1. Lobster muscles contain a latent multicatalytic proteinase; heating at 60 degrees C for 1-2 min converts the latent form to a heat-activated form with enhanced proteolytic activity. Both forms have three endopeptidase activities, which are classified as the trypsin-like, chymotrypsin-like, and peptidylglutamylpeptide bond hydrolyzing activities. 2. Sulfhydryl reagents (mersalyl acid, N-ethylmaleimide, hemin, iodoacetamide, and p-chloromercurisulfonic acid), benzamidine, and chloromethyl ketones inhibited all three activities of the heat-activated form. Leupeptin and antipain inhibited only the trypsin-like activity, while the chymotrypsin-like activity was the most sensitive to diisopropyl fluorophosphate, phenylmethanesulfonyl fluoride, aprotinin, and soybean trypsin inhibitor. Pepstatin and L-trans-epoxysuccinylpeptides had little effect on the peptidase activities. 3. Sodium dodecyl sulfate and oleic acid preferentially activated the peptidylglutamyl-peptide hydrolyzing activity of the latent form, whereas N-ethylmaleimide stimulated both the trypsin-like and peptidylglutamyl-peptide hydrolases. These results suggest that the lobster enzyme is an atypical serine proteinase.
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PMID:Differential effects of oleic acid, sodium dodecyl sulfate, and protease inhibitors on the endopeptidase activities of the lobster multicatalytic proteinase. 176 21

A tissue-kallikrein-related proteinase present in rat submaxillary glands, which was previously called endopeptidase k, has been further characterized and compared with other members of the kallikrein family. The partial primary structure of this proteinase, now called kallikrein k10, is very similar to that of proteinase B [Kato, H., Nakanishi, E., Enjyoji, K., Hayashi, I., Oh-Ishi, S. & Iwanaga, S. (1987) J. Biochem. (Tokyo) 102, 1389-1404] and T-kininogenase [Xiong, W., Chen. L. M. & Chao, J. (1990) J. Biol. Chem. 265, 2822-2827], but no corresponding gene or mRNA has so far been found. Kallikrein k10 is microheterogeneous due to variable glycosylation of its N-terminal light chain and to variable processing at its kallikrein loop, as shown by endo-beta-N-acetylglucosaminidase F treatment, amino acid sequence analysis and mass spectrometry. The enzymatic properties of the two molecular varieties of kallikrein k10 towards synthetic fluorogenic substrates are not significantly different. Both cleave specifically after Arg residues, but, in contrast to true tissue kallikrein, may accommodate either polar or nonpolar residues at position P2. Kallikrein k10 also differs from tissue kallikrein by its sensitivity to soyabean trypsin inhibitor. Its biological function may therefore differ from that of tissue kallikrein, especially as it does not induce a transient decrease in blood pressure when injected in vivo.
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PMID:Microheterogeneity of rat submaxillary gland kallikrein k10, a member of the kallikrein family. 202 64

N-Methyl-N-nitrosourea (MNU)-induced rat mammary adenocarcinomas contain high levels of a novel leupeptin-sensitive serine endopeptidase. Its properties apparently differ from those of other similar endopeptidases reported to be present in various normal and malignant mammalian tissues. The same leupeptinsensitive serine endopeptidase was also detected in normal rat mammary tissues, but at levels approximately 20 times lower than those in MNU-induced mammary tumors. This enzyme, which is a trypsin-like serine endopeptidase, preferentially hydrolyzes various synthetic endopeptidase substrates at the carboxyl side of an arginyl residue. It has an apparent Mr of approximately 160,000 and a Stokes radius of 49 A, as determined by gel filtration. Its isoelectric points range from 4.5 to 4.8, and it has a pH optimum of approximately 7.0. The enzyme is stable from pH 4.0 to 7.0, but is extremely unstable above pH 7.0. Besides leupeptin, its activity is inhibited by antipain, aprotinin, N alpha-p-tosyl-L-lysine chloromethyl ketone and phenylmethylsulfonyl fluoride, but is not inhibited by soybean trypsin inhibitor. Many other potential inhibitors or activators such as 2-mercaptoethanol, p-hydroxymercuribenzoic acid and EDTA have no effect on its activity. The enzyme is adsorbed to p-aminobenzamidine agarose affinity beads at pH 6.5 and elutes at pH 4.0.
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PMID:A novel leupeptin-sensitive serine endopeptidase present in normal and malignant rat mammary tissues. 216 30

A nonlysosomal alkaline protease which degrades the oxidatively modified form of Escherichia coli glutamine synthetase has been purified to apparent homogeneity from rat and mouse liver acetone powders. Its molecular weight was determined to be 300,000 by Sephacryl S-300 gel filtration but results of further studies using high pressure liquid chromatography gel filtration suggest a value of 650,000. Examination of the subunit structure by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed multiple bands of molecular weights between 22,000 and 34,000. The alkaline protease was inhibited by thiol reagents. Phenylmethylsulfonyl fluoride, aprotinin, leupeptin, antipain, and chymostatin partially inhibited the protease. The inhibition by phenylmethylsulfonyl fluoride was prevented by dithiothreitol, and alpha 1-antitrypsin and soybean trypsin inhibitor did not inhibit. No inhibition was observed with metalloprotease inhibitors. The alkaline protease is active over a broad range of pH with optimum activity for the degradation of oxidized glutamine synthetase around pH 9.0. Its activity is not stimulated by MgATP. A study of the products of insulin B chain degradation demonstrated major cleavage sites at Gln13-Ala14, Leu15-Tyr16, Cys(SO3H)19-Gly20, Gln4-His5, and Leu17-Val18. Based on its endopeptidase activity and its inhibitor specificity, the alkaline protease should be classified as a cysteine proteinase. It appears to be distinct from previously described proteinases and is likely involved in nonlysosomal mechanisms of intracellular protein turnover.
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PMID:Purification of a liver alkaline protease which degrades oxidatively modified glutamine synthetase. Characterization as a high molecular weight cysteine proteinase. 286 41

Parathyroid hormone (PTH) -degrading activity was studied using osteoblast-like UMR-106 cells. PTH-degrading activity was assessed by the amount of PTH fragments produced in the medium after exposure of intact human PTH-(1-84) to UMR-106 cells. PTH immunoreactivity recovered in trichloroacetic acid-soluble products of the medium and in fractions eluted from reverse-phase high-performance liquid chromatography (HPLC) was measured by radioimmunoassay using an antibody specific for the mid-region and C-terminus of PTH. In this study, intact UMR-106 cells but not extracellular enzymes cleaved human PTH(1-84) into fragments which were released into the medium (in a time- and temperature-dependent fashion). HPLC analysis of the PTH fragments depicted three immunoreactive peaks (peaks 1, 2 and 3) besides intact PTH, indicating a limited PTH-hydrolyzing activity of the cells. Furthermore, a 1000-fold molar excess of either hPTH-(3-34) or [Nle8,Nle18,Tyr34]hPTH-(3-34)amide inhibited PTH-degrading activity by 63% and 80% of control, respectively, whereas neither calcitonin, vasopressin nor growth hormone suppressed it. Additionally, HPLC analysis of the samples treated with [Nle8,Nle18,Tyr34]hPTH-(3-34)amide showed a reduction of the three peaks, suggesting an involvement of PTH receptor in the production of PTH fragments. This PTH-degrading activity was strongly inhibited by phenylmethylsulfonyl fluoride and chymostatin, but not by soybean trypsin inhibitor, elastatinal or inhibitors of cysteine, aspartic or metalloproteinases, indicating that it is due to a seryl chymotrypsin-like endopeptidase. Chymotrypsin-like activity seems to be solely responsible for PTH-degrading activity in intact UMR-106 cells, since all three PTH fragments were predominantly suppressed in the presence of chymostatin. Further analysis of chymotrypsin-digested products of hPTH-(1-84) eluted from HPLC exhibited five fragments detected by ultraviolet absorbance at 210 nm, three of which were measurable by PTH radioimmunoassay, each corresponding to the three PTH fragments produced by UMR-106 cells. To explore the cleavage sites of PTH further, amino acid analysis of chymotrypsin-cleaved products was performed. The results strongly support the view that the chymotrypsin-like enzyme in UMR-106 cells cleaved the hormone between residues 23-24 and 34-35, to produce, at least, hPTH-(24-84) and -(35-84). Our present study indicates that a chymotrypsin-like endopeptidase is solely responsible for limited hydrolysis of PTH by intact UMR-106 cells.
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PMID:Parathyroid hormone degradation by chymotrypsin-like endopeptidase in the clonal osteogenic UMR-106 cell. 291 1

Cathepsin-D has been previously reported to cleave intact PTH into PTH-(1-34) and -(35-84) in membranous fractions of rat and bovine kidney. Whether PTH degradation occurs by intact kidney cells, however, has not been examined in detail. We have, therefore, examined this possibility using an opossum kidney (OK) cell line which possesses the characteristics of proximal renal tubules and responds to PTH. PTH radioimmunoreactivity recovered in trichloroacetic acid-soluble products and in fractions eluted from reverse phase HPLC was measured using an antibody directed to the midregion and C-terminus of PTH. In this study, intact OK cells, but not extracellular enzymes, cleaved human (h) PTH-(1-84) into three discrete fragments which were released into the medium in a time- and temperature-dependent fashion. Half-maximal velocity of PTH-degrading activity (PTHDA) was observed at 9 nM hPTH-(1-84). A 1000-fold molar excess of PTH antagonists [hPTH-(3-34) and [Tyr34]hPTH-(7-34)amide] markedly inhibited PTHDA, whereas ACTH, glucagon, or big gastrin did not suppress it, suggesting an involvement of the PTH receptor in PTHDA. This PTHDA was strongly inhibited by phenylmethylsulfonylfluoride and chymostatin, but not by trypsin inhibitor, elastatinal, or inhibitors of aspartic, cysteine, or metalloproteinases, suggesting that it is due to a seryl chymotrypsin-like endopeptidase. Analysis of chymotrypsin-digested products of hPTH-(1-84) eluted from HPLC exhibited five fragments detected by UV absorbance (210 nm), three of which were measurable by PTH RIA, and each corresponded to the three PTH fragments produced by OK cells. All three fragments were predominantly suppressed in the presence of chymostatin, suggesting that chymotrypsin-like activity is solely responsible for PTHDA in intact OK cells. To further explore the cleavage sites of PTH by chymotrypsin, amino acid analysis of chymotrypsin-cleaved products was performed. The results strongly support the conclusion that a chymotrypsin-like enzyme in OK cells cleaved the hormone between residues 23-24, and 34-35 to produce, at least, hPTH-(24-84) and -(35-84). Lysosomal blockers (chloroquine, ammonium chloride, or monensin) did not affect this PTHDA. Our present study indicates that chymotrypsin-like endopeptidase, but not other endopeptidase or lysosomal enzymes, is responsible for the limited hydrolysis of PTH by intact OK cells.
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PMID:Parathyroid hormone degradation by chymotrypsin-like endopeptidase in the opossum kidney cell. 305 60


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