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)

Protease activity was detected in membranes of human bovine erythrocytes prepared by the conventional procedures which include washing and removal of the "buffy layer". The enzyme was extracted by 0.75 M KCNS or (NH4)2SO4 and was activated by 0.4 to 0.5 M of the same salts. Colored, particulate hide powder-azure, membrane fractions and soluble proteins such as hemoglobin, casein or albumin were susceptible to hydrolysis by the membraneous protease. Partial purification of the enzyme was accomplished through disc-gel electrophoresis on polyacrylamide in the presence of 0.25% positively charged detergents like cetyltrimethylammonium bromide. An alkaline protease (pH 7.4) with properties similar to those of the erythrocyte enzyme was found in leucocytes. The similarity between the properties of the leucocytic and erythrocytic proteases and the correlation of the activity in erythrocyte membranes with content of white cells in these preparations, suggest that enzymatic activities in the contaminating leucocytes are responsible for the activity of membraneous proteases in erythrocytes.
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PMID:Membrane-bound enzymes. III. Protease activity in leucocytes in relation to erythrocyte membranes. 0 92

The sequence of the amino-terminal 349 residues of rabbit muscle glycogen phosphorylase (EC 2.4.1.1) has been determined. Limited proteolysis of native phosphorylase b (841 residues, subunit molecular weight 97 412) by subtilisin BPN', Streptomyces alkaline protease, or elastase yielded two large segments (light and heavy). The light segment isolated from the subtilisin digest was cleaved at methionyl bonds with cyanogen bromide to yield eight major fragments and two minor overlapping fragments. The alignment of the major fragments was obtained by analysis of the two minor fragments, of five tryptic peptides containing methionine and of one large fragment generated by cleavage of an aspartylproline bond. Analysis of two cyanogen bromide fragments (CB14 and CB17) isolated from the intact molecule identified the sites susceptible to limited proteolysis and the overlap between the light and the heavy segments. Serine-14 and tyrosine-155 were identified as the residues involved in the covalent and allosteric controls of the enzyme, respectively. Residues 108 and 142 were identified as the cysteine residues reported to be involved in the aggregation of subunits.
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PMID:Sequence of the amino-terminal 349 residues of rabbit muscle glycogen phosphorylase including the sites of covalent and allosteric control. 72 24

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

Proteasomes (multicatalytic proteinase complexes) from rat liver are composed of at least 13 nonidentical components [Tanaka, K., Yoshimura, T., Ichihara, A., Ikai, A., Nishigai, M., Morimoto, M., Sato, M., Tanaka, N., Katsube, Y., Kameyama, K., & Takagi, T. (1988) J. Mol. Biol. 203, 985-996]. The nucleotide sequence of one major component (C2) of the proteasomes has been determined from a recombinant cDNA clone isolated by screening a rat liver cDNA library with a mixture of synthetic deoxyribonucleotides as a probe. The sequence was composed of 1174 nucleotides including a coding region for the entire protein and noncoding regions of both the 5'- and 3'-sides. The polypeptide deduced from the open reading frame consisted of 263 amino acid residues, and its molecular weight was calculated to be 29,516. The partial amino acid sequences of several fragments (approximately 45% of the total residues), which were obtained by cleavage of C2 with lysyl endopeptidase and cyanogen bromide, were determined by automated Edman degradation and found to be in complete accordance with those deduced from the cDNA sequence. The amino acid composition of C2, determined by chemical analysis, was also consistent with that deduced from the cDNA sequence, indicating that the cloned cDNA actually encoded component C2. Computer analysis revealed little structural similarity of C2 to other proteins reported so far. Northern blot hybridization analyses showed that the mRNA encoding this novel protein C2 was expressed in all the rat tissues examined and in a variety of eukaryotic organisms such as amphibia, birds, and mammals with slight species-specific differences in size.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Molecular cloning of cDNA for proteasomes (multicatalytic proteinase complexes) from rat liver: primary structure of the largest component (C2). 281 72

The role of proteasomes, particles with latent multicatalytic proteinase, in ATP-dependent proteolysis in rat reticulocyte extracts was examined. Removal of proteasomes from the extracts by immunoprecipitation caused almost complete inhibition of ATP-dependent degradation of [3H]methylcasein, without affecting ATP-dependent proteolysis. Peptide fragments of [3H]casein, obtained by cyanogen bromide cleavage, were rapidly degraded in an ATP-independent fashion and this activity was not affected by removal of the proteasomes. These results suggest that proteasomes are involved in ATP-dependent proteolysis in the extracts and that they catalyze the initial cleavage of large proteins.
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PMID:Involvement of proteasomes (multicatalytic proteinase) in ATP-dependent proteolysis in rat reticulocyte extracts. 304 62

The balance between the hepatic assembly of apolipoprotein B (apoB) and its presecretory degradation at the level of the endoplasmic reticulum (ER) may control the secretion of apoB-containing lipoproteins. In one model, apoB that fails to assemble with lipid undergoes translocation arrest, exposing the protein to the cytosolic proteasome. To examine apoB's translocation behavior under various metabolic conditions, glycosylation site utilization studies were performed. A 70-amino acid peptide containing three sites for N-linked glycosylation was appended to the C-terminus of apoB-50 (amino-terminal 50% of apoB) and expressed in both hepatic and nonhepatic cell lines. When the C-terminal reporter peptide was released by cyanogen bromide cleavage, all of the sites were glycosylated irrespective of cell type, labeling time, or assembly status. Similar peptide mapping of endogenous apoB-100 expressed in HepG2 cells was performed to monitor glycosylation at Asn residues 2752 (apoB-61), 2955 (apoB-65), and 3074 (apoB-68). N-linked glycosylation occurred at a minimum of two of the three sites, a frequency identical to that observed in apoB-100 recovered from cell media. Treatment of cells with proteasome inhibitors produced a 2. 5-fold increase in intracellular apoB but failed to cause accumulation of an unglycosylated form. These results indicate that 1) the efficient translocation of apoB into the ER occurs independently of microsomal triglyceride transfer protein and its assembly with lipid and 2) despite its large size and affinity for lipid, delivery of misassembled apoB to the proteasome requires retrograde translocation from the ER lumen to cytosol.
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PMID:Efficient glycosylation site utilization by intracellular apolipoprotein B. Implications for proteasomal degradation. 1058 47

A 46-year-old patient developed amyotrophic lateral sclerosis (ALS) characterized by rapid progression. She needed respiratory assistance after a course of 9 months. She died 4.5 years after onset. Autopsy showed dramatic atrophy of the spinal cord, sparing only the posterior tracts, associated with neuronal loss and astrogliosis in various areas including the anterior horns, motor cortex, striatum, thalamus, and substantia nigra. Ubiquitin immunohistochemistry showed rare skein-like inclusions in the surviving spinal and medullary motor neurons. Eosinophilic inclusions were found in the nuclei of pyramidal neurons in the hippocampus. These inclusions were immunoreactive to antibodies against ubiquitin, promyelocytic leukemia gene product, proteasome, and ataxin-3. They were not immunoreactive to antibodies against tau, cystatin C, neurofilament, alpha-synuclein, SOD-1, and polyglutamine (1C2), and were not stained by ethidium bromide. Similar inclusions were found in the motor cortex. The immunoreactivity of the inclusions was similar to that encountered in diseases associated with CAG repeats, except for the negativity of the immunolabelling with 1C2. At the ultrastructural level, the nuclear inclusions were made of straight filaments (10-12 nm in diameter) arranged at random, reminiscent of the polyglutamine intranuclear hyaline inclusions.
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PMID:Amyotrophic lateral sclerosis with neuronal intranuclear protein inclusions. 1511 87

Chalcones and their derivatives have been shown to have potent anticancer activity. However, the exact mechanisms of cytotoxic activity remain to be established. In this study, we have evaluated a series of boronic chalcones for their anticancer activity and mechanisms of action. Among the eight chalcone derivatives tested, 3,5-bis-(4-boronic acid-benzylidene)-1-methyl-piperidin-4-one (AM114) exhibited most potent growth inhibitory activity with IC50 values of 1.5 and 0.6 microM in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and colony formation assay, respectively. The cytotoxic activity of AM114 was shown to be associated with the accumulation of p53 and p21 proteins and induction of apoptosis. Mechanistic studies showed that AM114 treatment inhibited the chymotrypsin-like activity of the 20S proteasome in vitro, leading to a significant accumulation of ubiquitinated p53 and other cellular proteins in whole cells. In vitro studies showed that AM114 did not significantly disrupt the interaction of p53 and murine double minute 2 protein. It is noteworthy that AM114 as a single agent was preferentially toxic to cells with wild-type p53 expression, whereas combination of this compound with ionizing radiation (IR) significantly enhanced the cell-killing activity of IR in both wild-type p53 and p53-null cells. Together, these results indicate that the boronic chalcone derivative AM114 induces significant cytotoxic effect in cancer cells through the inhibition of the cellular proteasome and provide a rationale for the further development of this class of compounds as novel cancer chemotherapeutic agents.
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PMID:A boronic-chalcone derivative exhibits potent anticancer activity through inhibition of the proteasome. 1663 37

Proteolytic activity was detected within polyhedra of the nuclear polyhedrosis virus of Spodoptera littoralis. The enzyme activity was detected by its ability to degrade the major structural polypeptide of polyhedra (polyhedrin). A quantitative assessment of activity was made by a radioassay technique using (3)H-labeled polyhedrin as the substrate. Of the structural components of polyhedra, virus particles showed the greatest specific proteolytic activity. Preparations of purified nucleocapsids were inactive. The virus particle enzyme displayed a temperature optimum for proteolysis of 30 to 40 degrees C and a pH optimum of 9.6. Its activity was inhibited by H(2+) and Cu(2+), but not by 2-mercaptoethanol. The enzyme was purified from detergent-treated virus particles by affinity column chromatography, using polyhedrin linked to cyanogen bromide-activated Sepharose. Three major envelope polypeptides (L107, L85, and L71) bound to the column at 4 degrees C, but after incubation at 31 degrees C, polypeptide L71 alone was eluted. The fractions containing this protein exhibited a specific enzyme activity more than 80-fold greater than that present in polyhedra. The possible significance of the alkaline protease, and other proteins with affinity for polyhedrin, is discussed.
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PMID:Alkaline protease associated with virus particles of a nuclear polyhedrosis virus: assay, purification, and properties. 1678 69

Salinosporamide A (NPI-0052; 3), a highly potent inhibitor of the 20S proteasome, is currently in phase I clinical trials for the treatment of cancer. During the course of purifying multigram quantities of 3 from Salinispora tropica fermentation extracts, several new salinosporamides were isolated and characterized, most of which represent modifications to the chloroethyl substituent at C-2. Specifically, 3 was isolated along with the known compound salinosporamide B (4), the previously undescribed methyl congener salinosporamide D (7), and C-2 epimers of 3 and 7 (salinosporamides F (9) and G (10), respectively). Salinosporamide I (13), in which the methyl group at the ring junction is replaced with an ethyl group, and the C-5 deshydroxyl analogue salinosporamide J (14), were also identified. Replacement of synthetic sea salt with sodium bromide in the fermentation media produced bromosalinosporamide (12), 4, and its C-2 epimer (11, salinosporamide H). In addition to these eight new salinosporamides, several thioester derivatives were generated semisynthetically. IC50 values for cytotoxicity against human multiple myeloma cell line RPMI 8226 and inhibition of the chymotrypsin-like (CT-L) activity of purified rabbit 20S proteasomes were determined for all compounds. The results indicate that thioesters may directly inhibit the proteasome, albeit with reduced potency compared to their beta-lactone counterparts.
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PMID:Salinosporamides D-J from the marine actinomycete Salinispora tropica, bromosalinosporamide, and thioester derivatives are potent inhibitors of the 20S proteasome. 1724 24


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