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)

An alkaline proteinase, previously identified in rat liver and heart, has been purified from the soluble fraction of human erythrocytes. The proteinase has an apparent molecular weight of 600 000 and is composed of eight subunits with molecular weights ranging from 32 000 to 21 000. The proteinase degrades both protein and synthetic peptide substrates with a broad pH optimum of 7.5-11.0. Among the synthetic peptides tested, tripeptides with arginine at the P1 position (e.g. Z-Val-Leu-Arg-4-methoxy-2-napthylamine and Boc-Leu-Gly-Arg-4-methylcoumarin-7-amide) are particularly good substrates. The proteinase appears to be sulfhydryl-dependent and is inhibited completely by mersalyl acid and by hemin; inhibitors of serine and metallo-type proteinases have no effect on proteinase activity. Interestingly, a variety of other proteinase inhibitors such as leupeptin, chymostatin and N-ethylmaleimide failed to completely inhibit protein-hydrolyzing activities of the enzyme. These results indicate that these activities may be accounted for by at least two different catalytic sites. Proteinase activity is stable in the presence of 1 M urea, 0.5% Triton X-100 or 0.03% SDS and is not affected by ATP. Based on the high molecular weight and sulfhydryl-dependence, we have named this proteinase macropain.
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PMID:Purification and characterization of a high molecular weight proteinase (macropain) from human erythrocytes. 353 Mar 30

A linoleic acid-sensitive protease, ingensin, was purified to homogeneity from human placenta. The physical properties of the placental ingensin were found to be very similar to those of skeletal muscle ingensin [Ishiura et al. (1985) FEBS Lett. 189, 119-123]. The purified ingensin was activated by linoleic acid and SDS. The linoleic acid-activated form was inhibited preferentially by divalent cations, whereas the SDS-activated form was inhibited by monovalent cations instead.
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PMID:Effects of linoleic acid and cations on the activity of a novel high-molecular weight protease, ingensin, from human placenta. 353 Aug 32

A high-molecular-mass protease, ingensin, was purified to homogeneity from rabbit reticulocytes by DEAE-cellulose, HPLC gel filtration, and hydroxyapatite chromatographies. By these procedures, ingensin activity was separated from the activities of two other unique aminopeptidases, one of which is activated by ATP. Ingensin had the following properties: the optimum activity was seen around pH 9.0 and at 50 degrees C; addition of 0.04% SDS and 1 mg/ml linoleic acid resulted in 8- and 4-fold increases in peptide-hydrolyzing activity, respectively. The molecular mass was found to be 700,000 +/- 100,000 daltons on gel filtration, but SDS electrophoresis revealed that the enzyme is composed of several subunits with molecular weights of less than 35,000. The N-terminal-blocked tyrosine- and arginine-MCA derivatives, but not Arg-MCA, were hydrolyzed rapidly by ingensin. The approximate Km values for the reaction of ingensin with Suc-Leu-Leu-Val-Tyr-MCA and Z-Ala-Arg-Arg-MCA were 0.32 and 0.12 mM, respectively. The degradation of several proteins in the reticulocyte extract was stimulated by the addition of SDS and linoleic acid. The activator concentrations necessary for stimulation of the protein hydrolysis are similar to those of the purified reticulocyte ingensin for synthetic substrates. Ingensin did not associate with either right-side-out or inside-out red cell membranes. These results suggest that ingensin is a cytosolic fatty acid-stimulated protease, which is involved in the protein turnover in reticulocyte extracts.
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PMID:Ingensin, a high-molecular-mass alkaline protease from rabbit reticulocyte. 353 97

A large fraction of the translationally repressed non-globin messenger RNA in duck erythroblasts is present in non-polyribosomal free mRNP structures which sediment in the 30-40-S range ('35 S'). In 0.5 M KCl, they form core complexes which show a pronounced peak at about 32 S containing mRNA and a discrete spherical RNP particle with a diameter of about 12 nm and the typical morphology of a prosome [H.-P. Schmid et al. (1984) EMBO J. 3, 29-34]. Buoyant density measurements and chromatography on oligo(dT)-cellulose indicate that this particle is bound to mRNA; it can be released from the mRNA by treatment of the free mRNP fraction with SDS. This prosome-like particle inhibits the translation of mRNA in vitro. It is composed primarily of multimers of a single 21-kDa protein and at least one species of RNA of about 80-100 nucleotides. It is resistant to dissociation by 2 M CS2SO4 and 1% SDS; the 21-kDa protein is not attacked by proteinase K unless the particle is extracted with phenol prior to treatment with the protease. The small RNA moiety of the particle hybridizes to the poly(A)-rich mRNA derived from the free mRNPs, as well as to polyribosomal mRNA. These data indicate that prosomes may serve to regulate mRNA translation; they show furthermore that prosome-like particles (about 600 kDa mass) may be built of up to 25 molecules of a single specific protein, rather than of the entire set of about 20 prosomal proteins previously identified.
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PMID:A new type of prosome-like particle, composed of small cytoplasmic RNA and multimers of a 21-kDa protein, inhibits protein synthesis in vitro. 369 21

A multicatalytic proteinase from rat skeletal muscle contains active site(s) catalysing the degradation of benzoyl-Val-Gly-Arg 4-methyl-7-coumarylamide, succinyl-Ala-Ala-Phe 4-methylcoumarylamide and [14C]methylcasein as well as benzyloxy-carbonyl-Leu-Leu-Glu 2-naphthylamide. These activities are 7-14-fold activated by 1 mM-sodium dodecyl sulphate. The activation leads to a higher susceptibility to the proteinase inhibitor chymostatin and to a lower ability to be inhibited and precipitated by antibodies raised against the non-activated enzyme. Since no changes in Mr or subunit composition were observed in the SDS-activated form, some conformational changes seem to occur during the activation step. More pronounced activation was observed in the presence of physiological concentrations of fatty acids; oleic acid at 100 microM concentrations stimulated the proteinase about 50-fold. In contrast with the non-activated proteinase, the activated enzyme considerably degrades muscle cytoplasmic proteins in vitro. Thus it is not unlikely that, in vivo, potential activators such as fatty acids can induce the multicatalytic proteinase to participate in muscle protein breakdown.
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PMID:Activation of the multicatalytic proteinase from rat skeletal muscle by fatty acids or sodium dodecyl sulphate. 389 Aug 40

Two forms of a neutral protease that catalyzed the hydrolysis of succinyl-Leu-Leu-Val-Tyr-MCA were isolated from porcine skeletal muscle cytosol by fractionation on DEAE-cellulose, hydroxyapatite and Sephadex G-100. The native enzyme had a molecular mass of above 1000 kDa. Peak A, which was eluted from hydroxyapatite at 50 mM phosphate, was activated 37-fold by the detergent, SDS, while peak B which was eluted at 150 mM phosphate, was activated only 2-fold. After dialysis against water, the B form showed restored ability to be activated by SDS (9.6-fold with 0.04% SDS). The activated peak B was extremely sensitive to divalent and monovalent cations such as Ca2+, Mg2+, Na+, K+ and NH+4 as well as protease inhibitors such as leupeptin, chymostatin and DFP. These results suggest that these proteases are generally latent in the cells and may be regulated by changes in the concentrations of cations in the cytosol. We call this new type of protease, ingensin.
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PMID:Isolation of two forms of the high-molecular-mass serine protease, ingensin, from porcine skeletal muscle. 389 52

The chromatin fraction of rat liver exhibited proteolytic activity caused by serine proteases, with maximal activity at pH 8 or 10. They were analyzed by affinity labeling with [3H]diisopropylfluorophosphate followed by SDS-polyacrylamide gel electrophoresis, and partially purified by gel filtration through Sepharose 6B after selective extraction from the chromatin fraction. The following results were obtained. 1. The chromatin fraction contained three DFP-binding proteins with molecular weights of 52,000, 25,000, and 15,000 daltons, and they were tentatively designated proteins A, B, and C, respectively. Unlike proteins A and B, protein C reacted with DFP more strongly at pH 10 than at pH 8. A greater part of protein B was present in the nucleoli, while the others were predominantly distributed in extra-nucleolar chromatin. 2. Proteins A and B were extracted from the chromatin fraction by 5 M urea and 0.7 M NaCl, respectively; while protein C was not extractable by either solution. Proteins A and B were further purified by gel filtration through Sepharose 6B. 3. Protein B was a neutral protease with a maximal activity for 3H-labeled ribosomal proteins at pH 8 and showed high specificity for basic proteins, such as histone and ribosomal proteins. Protein A was an alkaline protease with a maximal activity at pH 10 and showed proteolytic activity not only for basic proteins but also for hydrophobic proteins, such as casein and non-histone proteins of chromatin. 4. Protein A was activated at pH 8 by high concentrations of NaCl, suggesting the presence of some inhibitor(s). Protein A was converted to protein C at pH 10, and also at pH 8 with high concentrations of NaCl. Thus, protein A is suggested to be the complex of protein C and unknown inhibitor(s). 5. When the chromatin fraction was incubated at pH 10, non-histone proteins were degraded much faster than at pH 8, although H1 histone was degraded at similar rates at both pHs. These results indicate that the chromatin fraction of rat liver contains at least two kinds of serine proteases, B and C, and that protease B is probably involved in the metabolism of basic protein, especially H1 histone. Protease C, the greater part of which associates with some inhibitors to form protein A, may play its main role in the metabolism of non-histone proteins.
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PMID:Studies on the serine proteases associated with rat liver chromatin. 675

Two proteolytic enzymes of Pseudomonas aeruginosa--an alkaline protease and an elastase--were incubated with human myeloma proteins IgG and IgA as well as with secretory IgA at 37 degrees C. Digest mixtures were analyzed after 1, 5, 12, 24, 48 and 72 h by SDS-polyacrylamide gel electrophoresis after reduction by 2-mercaptoethanol. Under conditions which resulted in cleavage of all three immunoglobulins by the elastase in the hinge-region, the alkaline protease cleaved only IgA. It was suggested that proteases of PA interfere with the immune-system of the host by cleavage of immunoglobulins. Elastase-positive PA strains should be more virulent compared with PA strains which produce only alkaline protease or are protease-negative at all.
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PMID:[Extracellular toxins of Pseudomonas aeruginosa. II. Effect of two proteases on human immunoglobulins IgG, IgA and secretory IgA (author's transl)]. 679 5

The multicatalytic endopeptidase complex (20S proteasome) is a latent high-molecular-mass multisubunit proteinase. In many investigations, SDS has been used as a proteasome activator at some fixed concentration that was apparently optimal. This study examined the effects of various divalent cations on the SDS-dependent peptidase and casein degradation activities of 20S proteasome purified from Xenopus laevis oocytes at a series of SDS concentrations and the correlation between these effects and the critical micelle concentration (CMC) of SDS. Surprisingly, it was found that divalent cations such as Mg2+ markedly shifted the SDS-dependent activation profiles to a lower concentration range. Ca2+, Mn2+, Co2+, and Zn2+ also markedly reduced the optimum SDS concentration in the Suc-Leu-Leu-Val-Tyr-MCA hydrolysis reaction: for example, 5 mM Co2+ reduced the optimum SDS concentration from 0.065 to 0.005%. However, in all cases examined the optimum concentrations were below the CMC. Cu2+, Hg2+, and Cd2+ strongly inhibited the SDS-dependent maximum activity without remarkably shifting the optimum SDS concentration. No correlation between the shift and the inhibition was recognized. Most interestingly, remarkable activation of casein degradation by SDS was observed only by addition of the divalent cations Mg2+, Ca2+, and Mn2+. These cations might be essential for casein degradation. The activation and inactivation ranges of SDS concentration varied with the species of substrate.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Reaction of 20S proteasome: shift of SDS-dependent activation profile by divalent cations. 749 Feb 55

Human decay-accelerating factor (DAF, CD55) is a phosphatidyl inositol-anchored glycoprotein consisting, from the N-terminus, of 4 short consensus repeats (SCR), a Ser/Thr (ST)-rich region providing O-glycosylation sites, and the membrane-anchoring unit. A mAb, named D17, was raised against purified erythrocyte-DAF. This mAb recognized DAF on blood cells and most cell lines as determined by flow cytometry and immunoblotting. Its reactivity was similar to but weaker than that of two other well-characterized mAbs to DAF, IA10 (seeing an epitope within SCR1) and 1C6 (seeing an epitope within SCR3). The reactivity of D17 with erythrocyte DAF became increased by treatment with sialidase/O-glycanase, suggesting that its epitope is located close to the O-glycosylation sites, probably within the ST-rich region or SCR4. D17 barely blocked the decay-accelerating activity of DAF. Using the three mAbs, tissue-associated and soluble forms of DAF were identified by SDS-PAGE/immunoblotting and immunohistochemical staining. IA10 and 1C6 recognized a 50 kDa protein in spermatozoa lysate and two proteins of Mr 70 and 55 kDa, respectively, in seminal fluid. These represented membrane-associated and soluble forms of DAF, which were neither recognized by mAb against membrane cofactor protein (MCP, CD46) and C3b/C4b receptor (CR1, CD35) nor by non-immune IgG. In contrast to IA10 and 1C6, D17 did not recognize either spermatozoa-DAF or seminal plasma-DAF, or the deglycosylated or untreated forms of them. Immunohistochemical analysis showed that testis was stained with IA10 but not with D17.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A monoclonal antibody against human decay-accelerating factor (DAF, CD55), D17, which lacks reactivity with semen-DAF. 750 2


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