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)

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

We have investigated the proteolytic degradation of [14C]methylcasein and 125I-labeled bovine serum albumin at pH 7.8 and 37 degrees C by lysates of rabbit reticulocytes purified from rabbit blood by two different procedures. (I) Lysates obtained from reticulocytes after removal of plasma and buffy coat as well as after washing of cells, degraded casein and albumin, and released from the two substrates 1.3%/h and 0.4%/h, respectively, of acid-soluble radioactivity. The activity towards both substrates was stimulated about 4-fold by ATP/Mg2+. Chromatography of whole blood on a column of cellulose prior to washing and lysis of cells had profound but differential effects on these activities in that stimulation of casein-degradation by ATP/Mg2+ was almost completely lost, whereas degradation of albumin, albeit at a low rate, was measurable in the presence of ATP/Mg2+ only. (II) Degradation of casein by these lysates is largely inhibited by a monospecific antibody against rabbit multicatalytic proteinase, whereas digestion of albumin is not affected by the antibody, either in the presence or absence of ATP/Mg2+. The latter activity is partially inhibited by a specific antibody against rabbit alpha 1-macroglobulin. (III) The immunoreactive amount of multicatalytic proteinase is about 1.2 micrograms per mg of lysate protein and almost identical in the two lysates. In contrast, the immunologically detectable levels of alpha 1-macroglobulin vary and are much lower in reticulocyte-lysates following chromatography on cellulose than in lysates from washed reticulocytes. (IV) Caseinolytic activity of multicatalytic proteinase, purified from rabbit reticulocyte lysate, is not activated by ATP/Mg2+ and the enzyme is proteolytically inactive towards albumin. On the other hand, a complex consisting of the proteinase inhibitor alpha 1-macroglobulin and the cysteine proteinase, cathepsin B, does degrade both substrates at pH 7.8, in an ATP/Mg2+-activated fashion. From these results it is concluded that the multicatalytic proteinase is an ATP-independent enzyme and a cellular constituent of rabbit reticulocytes whereas the activity stimulated by ATP/Mg2+ appears to be associated, at least in part, with a cysteine proteinase complexed to alpha 1-macroglobulin.
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PMID:High-molecular-mass proteinases in rabbit reticulocytes: the multicatalytic proteinase is an ATP-independent enzyme and ATP-activated proteolysis is in part associated with a cysteine proteinase complexed to alpha 1-macroglobulin. 247 Apr 11

Eukaryotic cells contain a 700-kDa proteolytic complex (the "proteasome" or multicatalytic endopeptidase complex), whose role in intracellular protein breakdown is unclear. It has been suggested that the proteasome functions in the rapid degradation of oxidant-damaged proteins and in the ATP-dependent proteolytic pathway. To test these possibilities, oxidant-damaged hemoglobin and albumin were produced by treating hemoglobin and albumin with phenylhydrazine, with hydroxyl radicals, or with both hydroxyl and superoxide radicals. After oxidant damage, these proteins were degraded more rapidly in erythrocyte extracts and also by the purified proteasome. However, complete removal of proteasomes from these extracts by immunoprecipitation (or inhibitors of its proteolytic activity) did not reduce the breakdown of oxidant-damaged hemoglobin and decreased degradation of hydroxyl- and superoxide-treated proteins by only 30-40%. Thus, erythrocytes must contain another proteolytic system for degradation of oxidant-damaged proteins. In contrast, immunoprecipitation of proteasomes with polyclonal or monoclonal antibodies prevented the ATP/ubiquitin-dependent degradation of lysozyme and also blocked the ATP-stimulated degradation of ubiquitin-conjugated lysozyme in reticulocyte and skeletal muscle extracts. These data indicate a critical role of the proteasome in the degradation of ubiquitin-conjugated proteins and suggest that the proteasome is associated with or is a component of the larger ubiquitin-conjugate-degrading enzyme complex.
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PMID:Involvement of the proteasome in various degradative processes in mammalian cells. 253 95

The multicatalytic proteinase purified from rat skeletal muscle was shown by electron microscopy to be a uniform cylinder-shaped protein particle. As the enzyme activities are enhanced by free fatty acids in vitro, we tested, by in vivo perfusion, whether high concentrations of free fatty acids increased the multicatalytic proteinase activities in skeletal muscle tissue. Perfusion of rat hindquarters with plasma containing 1.5 mM oleic acid bound to albumin led to a 30-40% increase of the proteinase activities in gastrocnemius muscle. This increase was statistically not significant when compared to control rats perfused with plasma containing fatty acid free albumin. These results are discussed under the following aspects: 1. the in vivo concentration of non-esterified fatty acids within the muscle cell is not known; 2. the uptake of free fatty acids by the muscle cell is too low, or the metabolism of free fatty acids taken up by the cell is too fast to allow activation of the multicatalytic proteinase; 3. the free fatty acids are bound to other proteins (e.g. fatty acid binding protein), which abolish their ability to activate the proteinase.
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PMID:Studies on the multicatalytic proteinase from rat skeletal muscle. 355 71

ATP-dependent proteolysis of 125I-labeled human alpha-globin, bovine alpha-lactalbumin, bovine serum albumin, or chicken lysozyme was assessed in a rabbit reticulocyte extract supplemented with ATP, excess ubiquitin, and variable amounts of ubiquitin aldehyde (Ubal), an inhibitor of many ubiquitin-protein isopeptidases. Low concentrations (0.8 microM) of Ubal increased the ATP-dependent degradation of 125I-alpha-globin by approximately 30% after 2 h at 37 degrees C, had little effect on 125I-lysozyme turnover, and decreased 125I-alpha-lactalbumin or 125I-albumin degradation by approximately 20%. The ATP-dependent degradation of all substrates was inhibited by high concentrations (> 3 microM) of Ubal throughout the incubation (15 min to 2 h); after 2 h, this inhibition ranged from 15% for 125I-alpha-globin to approximately 85% for 125I-alpha-lactalbumin and 125I-albumin. Levels of ubiquitin-125I-protein conjugates were increased significantly with Ubal; with > or = 8.0 microM Ubal, high molecular mass multiubiquitinated conjugates were particularly evident for 125I-alpha-globin and 125I-alpha-lactalbumin. These mixtures also accumulated ubiquitin conjugates with sizes expected for di- through pentaubiquitin oligomers. The results are consistent with the following proposed events: The ATP-dependent degradation of 125I-alpha-lactalbumin or 125I-albumin is probably mediated almost exclusively through polyubiquitinated intermediates. High Ubal concentrations inhibit an isopeptidase(s) which normally disassembles "unanchored" polyubiquitin chains that remain after substrate degradation by the 26S proteasome; these chains accumulate to inhibit further conjugate degradation. Much of the ATP-dependent degradation of 125I-alpha-globin and, to a lesser degree, 125I-lysozyme may occur through alternative structures where ubiquitin monomers or short oligomers are ligated to one or more substrate lysines. For 125I-alpha-globin, even low concentrations of Ubal effectively inhibit deubiquitination of these conjugates to enhance alpha-globin degradation.
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PMID:Differential effects of ubiquitin aldehyde on ubiquitin and ATP-dependent protein degradation. 871 81

Recent studies have suggested that activation of the ubiquitin-proteasome pathway is primarily responsible for the rapid loss of muscle proteins in various types of atrophy. The present studies were undertaken to test if different classes of muscle proteins are degraded by this pathway. In extracts of rabbit psoas muscle, the complete degradation of soluble proteins to amino acids was stimulated up to 6-fold by ATP. Peptide aldehyde inhibitors of the proteasome or the removal of proteasomes markedly inhibited only the ATP-dependent process. Addition of purified myosin, actin, troponin, or tropomyosin to these extracts showed that these proteins served as substrates for the ubiquitin-proteasome pathway. By contrast, degradation of myoglobin did not require ATP, proteasomes, or any known proteases in muscles. When myosin, actin, and troponin were added as actomyosin complexes or as intact myofibrils to these extracts, they were not hydrolyzed at a significant rate, probably because in these multicomponent complexes, these proteins are protected from degradation. Accordingly, actin (but not albumin or troponin) inhibited the degradation of 125I-myosin, and actin was found to selectively inhibit ubiquitin conjugation to 125I-myosin. Also, the presence of tropomyosin inhibited the degradation of 125I-troponin. However, neither actin nor tropomyosin inhibited the degradation of 125I-lysozyme or soluble muscle proteins. Thus, specific interactions between the myofibrillar proteins appear to protect them from ubiquitin-dependent degradation, and the rate-limiting step in their degradation is probably their dissociation from the myofibril.
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PMID:Importance of the ATP-ubiquitin-proteasome pathway in the degradation of soluble and myofibrillar proteins in rabbit muscle extracts. 890 Jan 46

Acute inflammation induces changes in liver proteins with an increase in synthesis of positive acute-phase proteins such as alpha1-acid glycoprotein (alpha1-AGP) and a decrease in synthesis of negative acute-phase proteins such as albumin. This is associated with muscle wasting, mediated by increased proteolysis and impaired protein synthesis. As protein metabolism can be altered in other situations (malnutrition, growth) by the form of the dietary nitrogen, we studied the effects of the molecular form of nitrogen on liver and skeletal muscle adaptation, looking at gene expression for two acute-phase proteins (albumin and alpha1-AGP) and a number of muscle proteins (alpha1-actin, ubiquitin and C9 proteasome subunit). Two groups of 24 Wistar rats (250 g) were injected S/C with 0.125 ml turpentine/rat and were fed one of two liquid diets. These diets had caloric, nitrogen, carbohydrate and lipid content but differed in the molecular form of the nitrogen source (whole protein [WP] versus peptide hydrolysate [PH]). Liver and muscle adaptation were studied at 18, 42 or 66 h after turpentine injection. Weight, deoxyribonucleic acid and protein content of the liver were significantly higher with the WP diet than with the PH diet at 42 h and 66 h. There was more alpha1-AGP messenger ribonucleic acid (mRNA) at 18 h and less albumin mRNA at 42 h. Thus, the PH diet causes a more rapid increase in alpha1-AGP mRNA content and a smaller decrease in albumin mRNA content after turpentine injection than the WP diet. However, the changes in plasma acute-phase proteins (albumin and alpha1-AGP) were similar with the two diets. In skeletal muscle, there was no change in mRNA levels for the C9 proteasome subunit at any time point with both diets compared to the controls. However, there were greater ubiquitin mRNA levels at 18|h and less alpha-actin mRNA levels at 18 h, 42 h and 66 h following turpentine injection in the two dietary groups than in the controls. These results suggest that the molecular form of nitrogen ingested regulates hepatic gene transcription or mRNA stability of acute-phase proteins, during the early period of inflammation, but did not affect the expression of muscle proteins, which was altered by turpentine injection. Post-transcriptional control of acute-phase protein genes may contribute to the maintenance of similar plasma levels.
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PMID:Effects of alimentary whole proteins versus their small peptide hydrolysates on liver and skeletal muscle during the acute inflammation phase in the rat. 1020 35

The intracellular concentration of the microsomal triglyceride transfer protein large subunit (lMTP), the abetalipoproteinemia gene product, is tightly controlled. To date, attempts at overexpressinglMTP in vivo or in vitro have been unsuccessful. We successfully overexpressed lMTP in HepG2 cells using an adenoviral vector containing an lMTP cDNA, AdMTP. AdMTP-transduced HepG2 cells overexpressed MTP activity. They secreted increased amounts of apoB-100 lipoproteins with LDL and HDL density into the medium. lMTP overexpression alone minimally changed the density profile of apoB-containing lipoproteins, but addition of oleic acid shifted the profile toward lower densities. Oleic acid had a greater stimulatory effect on apoB-100 secretion in control HepG2 cells than in AdMTP-transduced cells, because (i) adenoviral transduction per se suppressed protein synthesis, affecting apoB-100 and albumin equally, and (ii) adenoviral transduction partially attenuated the increase in triglyceride synthesis in response to oleic acid supplementation. AdMTP treatment greatly diminished the intracellular degradation of apoB-100, but in comparison with recombinant virus containing luciferase cDNA (AdLuc), it caused no change in its biosynthetic rate. It greatly reduced, but did not eliminate, its proteasomal degradation. Our study constitutes the initial demonstration that adenovirus-mediated transfer of lMTP markedly stimulates MTP expression which in turn stimulates apoB-100 production. The mechanism involves a downregulation of ubiquitin-proteasome-mediated degradation without any change in synthetic rate.
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PMID:Adenovirus-mediated overexpression of microsomal triglyceride transfer protein (MTP): mechanistic studies on the role of MTP in apolipoprotein B-100 biogenesis. 1036 Sep 51

The uppermost superficial surface layer of articular cartilage, the 'lamina splendens' which provides a very low friction lubrication surface in articular joints, was investigated using atomic force microscopy (AFM). Complementary specimens were also observed under SEM at -10 degrees C without dehydration or sputter ion coating. Fresh adult pig osteochondral specimens were prepared from the patellas of pig knee joints and digested with the enzymes, hyaluronidase, chondroitinase ABC and alkaline protease. Friction coefficients between a pyrex glass plate and the osteochondral specimens digested by enzymes as well as natural (undigested) specimens were measured, using a thrust collar apparatus. Normal saline, hyaluronic acid (HA) and a mixture of albumin, globulin, HA (AGH) were used as lubrication media. The surface irregularities usually observed in SEM studies were not apparent under AFM. The articular cartilage surface was resistant to hyaluronidase and also to chondroitinase ABC, but a fibrous structure was exhibited in alkaline protease enzymes-digested specimens. AFM analysis revealed that the thickness of the uppermost superficial surface layer of articular cartilage was between 800 nm and 2 microm in adult pig articular cartilage. The coefficient of friction (c.f.) was significantly higher in chondroitinase ABC and alkaline protease enzymes digested specimens. Generally, in normal saline lubrication medium, c.f. was higher in comparison to HA and AGH lubrication media. The role of the uppermost, superficial surface layer of articular cartilage in the lubrication mechanism of joints is discussed.
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PMID:Role of uppermost superficial surface layer of articular cartilage in the lubrication mechanism of joints. 1155 3

Low values of serum proteins and loss of lean body mass are commonly found in patients with chronic renal insufficiency (CRI) and especially in dialysis patients. These abnormalities have been attributed to malnutrition (i.e., an inadequate diet), but available evidence indicates that this is not the principal cause. In contrast, there is persuasive evidence that secondary factors associated with the CRI condition cause abnormalities in protein turnover and ultimately result in low serum protein levels and loss of lean body mass. Recent reports have identified some factors that could interfere with the control of protein turnover in CRI patients, including acidosis, inflammation, and/or resistance to anabolic hormones. Each of these stimulates protein breakdown in muscle and activates a common proteolytic pathway, the ubiquitin-proteasome pathway. Moreover, acidosis or inflammation suppress hepatic albumin synthesis. Understanding the biochemical mechanisms that regulate the ubiquitin-proteasome and other catabolic pathways are required to identify new strategies for preventing protein deficits that are associated with CRI.
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PMID:Insights into the abnormalities of chronic renal disease attributed to malnutrition. 1179 58


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