Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.25.1 (proteasome)
28,817 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

When dialyzed extracts from hake (Merluccius hubbsi) skeletal muscle were chromatographed in DEAE-Sephacel, an alkaline protease (37 degrees C, pH 8.5) and a trypsin inhibitor were isolated. The enzyme showed its maximal activity against azocasein in the range of pH between 7 and 9. The protease was able to hydrolyze the trypsin substrates Bz-Arg-OEt and Tos-Arg-OMe and did not cleave the chymotrypsin substrate Bz-Tyr-OEt. The enzyme was strongly inhibited by several serine protease inhibitors, whereas inhibitors of the other types of proteases scarcely affected it. The protease was able to degrade the major contractile and cytoskeletal constituent proteins of myofibrils and to accumulate acid-soluble products. The protease activity was completely suppressed by the addition of the trypsin inhibitor isolated from the same muscle. These results indicate that hake skeletal muscle contains a trypsin-like serine protease which might be involved in the catabolism of myofibrillar proteins, as well as in the proteolytic events that take place during post mortem storage of fish muscle.
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PMID:Detection of a trypsin-like serine protease and its endogenous inhibitor in hake skeletal muscle. 189 57

Proteasome, a high molecular weight multicatalytic protease, was purified from the cytosolic fraction of human platelets for the first time. The biochemical properties of the enzyme including substrate specificity, optimal pH and effects of various inhibitors were almost identical with those of other cells. During the purification with a Heparin-Sepharose chromatography, a novel endogenous activator of the protease was identified and was partially purified. The activator enhanced both chymotrypsin or trypsin like activities of the proteasome in a dose related manner and was inactivated by heating at 56 degrees C for 30 min. This newly identified activator may serve as an important regulator or cofactor of intracellular activities of the proteasome.
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PMID:Proteasome and its novel endogeneous activator in human platelets. 206 66

Chicken liver multicatalytic proteinase is composed of multiple components with molecular masses ranging from 23 to 34 kDa and has 'chymotrypsin-like' and 'trypsin-like' activities, which were examined by using the chromogenic peptide substrates, succinyl-Phe-Leu-Phe-pNA(p-nitroanilide) and N-benzoyl-Phe-Val-Arg-pNA, respectively. Treatment of the enzyme with diisopropyl fluorophosphate (DFP) completely abolished the 'chymotrypsin-like' activity, but had little effect on the 'trypsin-like' activity. In the experiment with radio-labeled DFP, SDS-PAGE of the modified enzyme revealed that the radioactivity was incorporated into only the smallest subunit (23 kDa). The migration of this subunit was retarded on SDS-PAGE after the treatment with DFP.
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PMID:'Chymotrypsin-like' activity of chicken liver multicatalytic proteinase resides in the smallest subunit. 226 74

The amino acid sequence of the neutral zinc protease from Bacillus mesentericus strain 76 (MCP 76) has been determined by using peptides derived from digests with trypsin, chymotrypsin, and cyanogen bromide and from cleavage with o-iodosobenzoic acid. The peptides were purified by means of gel filtration and reversed-phase high-performance liquid chromatography and analyzed by automatic sequencing. The protein contains 300 amino acid residues. It proved to be identical with the neutral protease deduced from the DNA precursor sequence of Bacillus subtilis. The residues for zinc and substrate binding are conserved, whereas the number of calcium binding sites is reduced compared to thermolysin. A classification of the neutral zinc protease is discussed.
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PMID:Primary structure of a zinc protease from Bacillus mesentericus strain 76. 230 86

We present here a detailed study of the effect of detergents on the three peptidase activities (hydrolysis of the LLVY, ARR, and LLE peptides) of the purified multicatalytic proteinase from rat liver. At Triton X-100 and sodium dodecyl sulfate (SDS) concentrations of 0.1%, all three peptidase activities are inhibited. Lower concentrations of the two detergents (0.01%) do not affect the hydrolysis of the ARR peptide, whereas they behave differently on the hydrolysis of the LLVY and LLE peptides. Triton X-100 inhibits and SDS strongly activates LLVY peptide hydrolysis by decreasing and increasing Vmax, respectively. In the absence of detergents, the saturation curve for the LLE peptide can be analyzed as the result of two components, one showing cooperative (nH = 1.6) with higher affinity (S0.5 = 60 microM) and lower Vmax than a second, noncooperative component (Km = 320 microM). SDS (0.01%) activates LLE peptide hydrolysis by suppressing cooperativity, slightly increasing Vmax, and decreasing the half-saturation concentration (Km = 30 microM) of the enzyme. Triton X-100 (0.01%) also suppresses the cooperativity and decreases the half-saturation concentration (Km = 25 microM) for the LLE peptide; in contrast, it reduces Vmax by inhibition of the low affinity, high Vmax component observed in the absence of detergents. Based on these observations, it can be concluded that both detergents behave like allosteric activators of peptidylglutamyl-peptide hydrolyzing activity and that the multicatalytic proteinase has at least three different classes of active sites: two independent noncooperative sites that catalyze the hydrolysis of trypsin and chymotrypsin-like substrates and one class for peptidylglutamyl-peptide hydrolysis having two components: one cooperative (two or more sites) and one noncooperative.
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PMID:Kinetic studies of the differential effect of detergents on the peptidase activities of the multicatalytic proteinase from rat liver. 238 Jan 98

Freshly isolated monocytes in suspension express 2000 to 4000 high affinity receptors for IFN-gamma. Because monocytes change phenotypically as they migrate out of the circulation and adhere to extracellular matrix, modulation of the expression of IFN-gamma receptors may occur. In order to determine if adherence alone modulates the receptor for IFN-gamma, we have studied receptor expression in adherent human peripheral blood monocytes. Elutriation-purified monocytes were allowed to adhere to polystyrene overnight at 37 degrees C. These cells now expressed 1 to 2 x 10(5) low affinity (Ka = 10(8) liters/M) receptors for [125I]rIFN-gamma. Binding to this receptor was specific and saturable. The expression of these receptors occurred rapidly (within 3 h) after adherence and was not inhibited by cycloheximide treatment. Binding to the receptor was abrogated by treating cells with trypsin, but was enhanced after treatment with alkaline protease or proteinase K. mAb against the high affinity receptor did not block binding to the low affinity receptor on adherent cells. The low affinity receptor transduced a signal to the cell as measured by the IFN-gamma-induced enhancement in FcR for human IgG1. The structure of the receptor on adherent cells was investigated by chemical cross-linking techniques. A receptor-[125I]rIFN-gamma complex was observed by SDS-PAGE to have a Mr of 180,000 to 200,000. Reduction of this complex with 2-ME resulted in the loss of the high Mr complex and the appearance of a doublet of lower Mr of 68,000 and 82,000. In contrast, cross-linking of monocytes in suspension yielded a complex of 110,000 to 120,000 Mr, which was unchanged upon reduction. Upon adherence, human monocytes express large numbers of a novel receptor for rIFN-gamma which is capable of stimulating the cell. This receptor appears to be composed of at least two components which are disulfide linked and structurally differs from the high affinity receptor on nonadherent monocytes.
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PMID:Characterization of a novel low affinity receptor for IFN-gamma on adherent human monocytes by radioligand binding studies and chemical cross-linking. 252 81

The 700-kDa multicatalytic proteinase complex from bovine pituitaries separates in polyacrylamide gel electrophoresis under dissociating and reducing conditions into 11 components with molecular masses ranging from 21 to 32 kDa. No higher molecular mass components were detected. A rabbit polyclonal antibody raised against the complex recognizes five immunoreactive components. As reported previously, the complex exhibits three distinct proteolytic activities designated as chymotrypsin-like, trypsin-like, and peptidylglutamyl-peptide hydrolyzing activities. All three activities are rather rapidly inactivated by 3,4-dichloroisocoumarin, a general serine protease inhibitor, however, the pseudo-first-order rate constants of inactivation of the three components differ within a wide range, with the chymotrypsin-like activity being most sensitive to inhibition. The peptidylglutamyl-peptide hydrolyzing activity is greatly activated by low concentrations of sodium dodecyl sulfate and fatty acids and seems to constitute the main component responsible for degradation of protein substrates. In addition to cleaving bonds on the carboxyl side of glutamyl residues, this activity also cleaves, albeit at a slower rate, bonds on the carboxyl side of hydrophobic residues; however, the secondary specificity of this component is clearly different from the chymotrypsin-like activity. Heparin selectively activates the chymotrypsin-like activity. The complex cleaves rapidly both native and dephosphorylated beta-casein in a reaction greatly accelerated by low concentrations of sodium dodecyl sulfate. The nature of proteolytic products, and also the rate of formation of acid-soluble, ninhydrin-reactive products, is different for the phosphorylated and dephosphorylated form of beta-casein, indicating that the degree of phosphorylation influences the rate and pattern of proteolysis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Pituitary multicatalytic proteinase complex. Specificity of components and aspects of proteolytic activity. 253 72

The presence of two distinct high-molecular-weight proteases with similar pH optima in the weakly alkaline region was shown in cytosol of the bovine brain cortex. They were separated by ammonium sulfate fractionation and each was further purified by DEAE-Sephacel, Sephacryl S-300, DEAE-Cibacron Blue 3GA-agarose, heparin-agarose, and Sepharose 6B chromatography. The larger enzyme (Mr 1,400 kDa), which precipitates at 0-38% ammonium sulfate saturation, seems to be active in ATP + ubiquitin (Ub)-dependent proteolysis; it has low basal caseinolytic activity that is stimulated 3-fold by ATP, and when Ub is present ATP causes a 4.5-fold stimulation. A second proteinase was also found to be present (Mr 700 kDa) that precipitates at 38-80% ammonium sulfate saturation, is composed of multiple subunits ranging in Mr from 18 to 30 kDa, and degrades both protein and peptide substrates, demonstrating trypsin-, chymotrypsin- and cucumisin-like activities. Catalytic, biochemical, and immunological characteristics of this proteinase indicate that it is a multicatalytic proteinase complex (MPC), whose enzyme activity, in contrast to that of MPC from bovine pituitaries (1-3), is stimulated 1.7-fold by addition of ATP in the absence of ubiquitin at the early steps of purification; this property is lost during the course of further purification. Both proteinases are present in the nerve cells, since the primary chicken embryonic telencephalon neuronal cell culture extracts contain both ATP + Ub-dependent proteinase and MPC activities.
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PMID:The presence of ATP + ubiquitin-dependent proteinase and multicatalytic proteinase complex in bovine brain. 255 23

It has been suggested that proteases are involved in removal of damaged or obsolete proteins and/or that the activation of proteases could contribute to cataract formation. This review summarizes the properties of several recently studied lens endopeptidases including: trypsin-like protease, multicatalytic endopeptidase complex, membrane bound proteases, and calpain. Properties discussed include composition, substrate specificity, distribution, changes in activity during aging, and regulation. Additionally, properties of the lens ubiquitin conjugation system are reviewed. When possible, an attempt was made to relate these findings to whether the lens proteolytic activity was involved in clearing damaged proteins, or whether it could contribute to cataract formation. Clearing of damaged or obsolete lens proteins may involve the participation of several protease activities. Findings suggest that lens protease activities are lost at variable rates during aging, and differ in concentration between species. It was concluded that the consequence of proteolytic activity in the lens may depend closely on the compliment of proteolytic activities found. For instance, proteases causing only partial degradation of lens proteins may predominate in lenses undergoing cataract formation, while proteases assisting in the removal of partially degraded proteins are lost. The partially degraded lens proteins, as well as other denatured lens proteins, may then accumulate and lead to cataract formation.
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PMID:Role of proteolysis in lenses: a review. 256 21

A high-molecular-weight (Mr 740,000) multicatalytic proteinase (MCP) was purified over 3100-fold from soluble extracts of lobster claw and abdominal muscles. The enzyme was extracted from muscle in a latent state; brief (3 min) heating of an ammonium sulfate fraction (45-65% saturation) at 60 degrees C irreversibly activated the proteinase while denaturing about 55% of the protein. MCP was further purified by chromatography on two sequential arginine-Sepharose columns and a Mono Q column with a yield of 60%. About 1.12 mg MCP was obtained for every 100 g tissue. In addition to [14C]methylcasein, the MCP hydrolyzed synthetic peptide substrates of trypsin and chymotrypsin at pH 7.75. Serine protease inhibitors (diisopropyl fluorophosphate, phenylmethanesulfonyl fluoride, aprotinin, benzamidine, soybean trypsin inhibitor, chloromethyl ketones), leupeptin, antipain, hemin, sulfhydryl-blocking reagents (N-ethylmaleimide, mersalyl acid, p-chloromercurisulfonic acid, iodoacetamide) suppressed activity while Ep-475, a specific inhibitor of cysteine proteinases, had no effect, suggesting the MCP is a serine proteinase with one or more cysteine residues indirectly involved in catalysis. The latent MCP was purified using the same procedure as that for the active form, except that thermal activation was omitted. The elution characteristics of latent MCP from the arginine-Sepharose and Mono Q columns were identical to those of active MCP. Since the purified latent form could still be activated by heating, activation did not involve denaturation of an endogenous inhibitor or substrate. Subunit compositions of both forms were identical in two-dimensional polyacrylamide gels; each was composed of eight polypeptides with molecular weights between 25,000 and 32,500 and a ninth polypeptide with a molecular weight of 41,000. Electron microscopy of negatively stained material showed that each form was a cylinder-shaped particle (approximately 10 x 15 nm) consisting of a stack of four rings with a hollow center; no differences in shape, dimensions, or submolecular structure were observed. These results suggest that activation probably involved small conformational changes rather than covalent modifications or rearrangement of subunits within the complex.
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PMID:Purification and characterization of a multicatalytic proteinase from crustacean muscle: comparison of latent and heat-activated forms. 267 43


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