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)

The present experiments have employed microelectrode techniques (pH and PCO2) and microcalorimetry (total CO2 concentration) to define parameters of acidification in specific structures of the rat testis and epididymis during control conditions and after administration of the carbonic anhydrase inhibitor acetazolamide (20 or 50 mg/kg). Values for in situ pH during control conditions in seminiferous tubules (ST; 6.96 +/- 0.01), proximal caput (PCP; 6.62 +/- 0.01), middle caput (MCP; 6.59 +/- 0.01), middle corpus (MCR; 7.10 +/- 0.02), and proximal cauda epididymidis (PCD; 6.85 +/- 0.01) were significantly more acidic than in testicular artery (TA; 7.36 +/- 0.01) or systemic arterial blood (SAB; 7.40 +/- 0.01) and did not change significantly after acetazolamide. In situ partial pressure of CO2 (PCO2) in TA (52.2 +/- 0.6 mmHg), ST (52.3 +/- 0.4 mmHg), PCP (52.9 +/- 0.4 mmHg), MCP (53.0 +/- 0.7 mmHg), MCR (53.4 +/- 0.4 mmHg), and PCD (52.4 +/- 0.4 mmHg) were indistinguishable from each other, but all values were significantly higher than SAB PCO2 (39.2 +/- 0.5 mmHg). Acetazolamide increased in situ PCO2 significantly in all structures except the MCR. The total CO2 concentration in normal ST fluid (10.7 +/- 0.5 mM) was significantly higher than in "primary" fluid (6.9 +/- 0.3 mM), and both values were well below TA (26.9 +/- 1.3 mM) or SAB (24.6 +/- 0.4 mM) total CO2 concentrations. In the epididymis, total CO2 concentrations were indistinguishable and not different from the value in primary fluid.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Direct evaluation of acidification by rat testis and epididymis: role of carbonic anhydrase. 210 57

The effect of CO2 on ethylene-induced gummosis (secretion of polysaccharides), weight loss and respiration in tulip bulbs (Tulipa gesneriana L.) was investigated. A pretreatment with 1-MCP prevented these ethylene-induced effects, indicating that ethylene action must have been directed via the ethylene receptor. Treatment with 0.3 Pa ethylene for 2 days caused gummosis on 50% of the total number of bulbs of cultivar Apeldoorn, known to be sensitive for gummosis. Addition of CO2 (10 kPa) reduced the ethylene-induced gummosis to 18%. In a second experiment the influence of ethylene and CO2 on respiration and FW loss of bulbs of the cultivar Leen van der Mark was studied. A range of ethylene partial pressures (0.003-0.3 Pa) was applied continuously for 29 days. Ethylene caused a transient peak in O2 consumption rate during the first days after the start of application. The relation between O2 consumption rate and ethylene partial pressure could be described by Michaelis-Menten kinetics. Respiratory peaks were reduced by CO2. This inhibition by CO2 could not totally be due to competition with ethylene at the receptor binding-site, as was indicated by the use of an O2 consumption model. Pre-treatment of bulbs with 1-MCP and subsequent exposure to CO2 showed that CO2 could influence respiration irrespective of any interaction with ethylene. Ethylene and CO2 both stimulated weight loss. The effect of combined treatments of ethylene and CO2 on weight loss was at least as strong as the sum of the separate effects, which implies that competition between ethylene and CO2 at the receptor binding-site was unlikely.
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PMID:Carbon dioxide and ethylene interactions in tulip bulbs. 1190 80

Ethylene production in pear fruit was studied at 2 degrees C. Several observations showed that the inhibiting effect of CO2 on ethylene production did not operate only via the binding site of the ethylene binding protein. Ethylene production of freshly harvested pears was stimulated by 1-methylcyclopropene (1-MCP), but unaffected or inhibited by CO2 which points to different action sites for both molecules. In climacteric pears, where ethylene production was strongly inhibited by 1-MCP, a range of applied CO2 partial pressures was able to inhibit ethylene production further, to an extent similar to untreated pears. In the case of pears that had been stored for a period of 25 weeks, CO2 only had a clear effect after 1-MCP pretreatment. Respiration measurements showed that the effect of CO2 on ethylene production did not operate via an effect on respiration. Ethylene production models based on measurements of whole pears were used to study CO2 effects. Kinetic parameters derived from the models point to the conversion from ACC to ethylene by ACC oxidase as a possible action site for CO2 inhibition.
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PMID:Carbon dioxide action on ethylene biosynthesis of preclimacteric and climacteric pear fruit. 1273 Feb 72

Fresh raw milks, with low (3.1 x 10(4) cell/ml) and high (1.1 x 10(6) cells/ml) somatic cell count (SCC), were standardized to 3.25% fat, and from each a preserved (with 0.02% potassium dichromate) and an unpreserved portion were prepared. Subsamples of each portion were carbonated to contain 0 (control, pH 6.9) and 1500 (pH 6.2) ppm added CO2, and HCl acidified to pH 6.2 Milk pH was measured at 4 degrees C. For the preserved low- and high-SCC milks, two additional carbonation levels, 500 (pH 6.5) and 1000 (pH 6.3) ppm, were prepared. Milks were stored at 4 degrees C and analyzed on d 0, 7, 14, and 21 for microbial count, proteolysis, and lipolysis. The addition of 1500 ppm CO2, but not HCl, effectively delayed microbial growth at 4 degrees C. In general, in both the low- and high-SCC unpreserved milks, there was more proteolysis and lipolysis in control and HCl acidified milks than in milk with 1500 ppm added CO2. Higher levels of proteolysis and lipolysis in the unpreserved milks without added CO2 were related to higher bacteria counts in those milks. In preserved low- and high-SCC milks, microbial growth was inhibited, and proteolysis and lipolysis were caused by endogenous milk enzymes (e.g., plasmin and lipoprotein lipase). Compared with control, both milk with 1500 ppm added CO2 and milk with HCl acidification had less proteolysis. The effect of carbonation or acidification with HCl on proteolysis in preserved milks was more pronounced in the high SCC milk, probably due to its high endogenous protease activity. Plasmin is an alkaline protease and the reduction in milk pH by added CO2 or HCl explained the reduction in proteolysis. No effect of carbonation or acidification of milk on lipolysis was observed in the preserved low- and high-SCC milks. The CO2 addition to raw milk decreased proteolysis via at least two mechanisms: the reduction of microbial proteases due to a reduced microbial growth and the possible reduction of endogenous protease activity due to a lower milk pH. The effect of CO2 on lipolysis was mostly due to a reduced microbial growth. High-quality raw milk (i.e., low initial bacteria count and low SCC) with 1500 ppm added CO2 can be stored at 4 degrees C for 14 d with minimal proteolysis and lipolysis and with standard plate count < 3 x 10(5) cfu/ml.
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PMID:Effect of CO2 addition to raw milk on proteolysis and lipolysis at 4 degrees C. 1277 72

In C4 photosynthesis, phosphoenolpyruvate carboxylase (PEPC) is the enzyme responsible for catalyzing the primary fixation of atmospheric CO2. The activity of PEPC is regulated diurnally by reversible phosphorylation. PEPC kinase (PEPCk), a protein kinase involved in this phosphorylation, is highly specific for PEPC and consists of only the core domain of protein kinase. Owing to its extremely low abundance in cells, analysis of its regulatory mechanism at the protein level has been difficult. Here we employed a transient expression system using maize mesophyll protoplasts. The PEPCk protein with a FLAG tag could be expressed correctly and detected with high sensitivity. Rapid degradation of PEPCk protein was confirmed and shown to be blocked by MG132, a 26S proteasome inhibitor. Furthermore, MG132 enhanced accumulation of PEPCk with increased molecular sizes at about 8 kDa intervals. Using anti-ubiquitin antibody, this increase was shown to be due to ubiquitination. This is the first report to show the involvement of the ubiquitin-proteasome pathway in PEPCk turnover. The occurrence of PEPCks with higher molecular sizes, which was noted previously with cell extracts from various plants, was also suggested to be due to ubiquitination of native PEPCk.
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PMID:The ubiquitin-proteasome pathway is involved in rapid degradation of phosphoenolpyruvate carboxylase kinase for C4 photosynthesis. 1569 55

Gala apples exposed to the ethylene action inhibitor 1-methylcyclopropene (1-MCP) for 12 h at 20 degrees C were stored at 1 degrees C in air or a controlled atmosphere (CA) maintained at 1 kPa O2 and 2 kPa CO2. Volatile compounds were measured after 4, 12, 20, and 28 weeks plus 1 or 7 days at 20 degrees C. Treatment with 1-MCP and then storage in air or CA or storage in CA without 1-MCP treatment reduced volatile production as compared to apples not treated with 1-MCP stored in air. The reduced production of esters, alcohols, aldehydes, acetic acid, and 1-methoxy-4-(2-propenyl)benzene was observed. Ester production by fruit stored in CA decreased throughout the storage period regardless of previous 1-MCP treatment. The production of esters, alcohols, aldehydes, acetic acid, and 1-methoxy-4-(2-propenyl)benzene by 1-MCP-treated fruit stored in air plus 7 days at 20 degrees C increased after 20 or 28 weeks of storage. Continuous exposure to 417 micromol m(-3) ethylene for 7 days at 20 degrees C after 12 or 28 weeks of storage stimulated production of many volatile compounds, primarily esters and alcohols, by fruit stored in CA or 1-MCP-treated apples stored in air. However, exposure to ethylene had no effect on the production of aldehydes or acetic acid.
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PMID:Interactive responses of gala apple fruit volatile production to controlled atmosphere storage and chemical inhibition of ethylene action. 1591 18

Hypoxia inducible factor (HIF) is an alpha/beta heterodimeric transcriptional complex that plays a key role in directing cellular responses to hypoxia. Recent studies have defined novel oxygen-sensitive signal pathways that regulate the activity of HIF by post-translational hydroxylation at specific residues within the alpha subunits. HIF prolyl hydroxylation regulates proteolytic degradation of HIF whereas HIF asparaginyl hydroxylation modulates interaction with transcriptional co-activators. These hydroxylations are catalysed by a set of non-haem Fe(II)- and 2-oxoglutarate (2-OG)-dependent dioxygenases. During catalysis, the splitting of molecular oxygen is coupled to the hydroxylation of HIF and the oxidative decarboxylation of 2-OG to give succinate and CO2. Hydroxylation at two prolyl residues within the central 'degradation domain' of HIF-alpha increases the affinity for the von Hippel-Lindau (pVHL) E3 ligase complex by at least three orders of magnitude, thus directing HIF-alpha polypeptides for proteolytic destruction by the ubiquitin/proteasome pathway. Since the HIF hydroxylases have an absolute requirement for molecular oxygen this process is suppressed in hypoxia allowing the HIF-alpha to escape destruction and activate transcription. Co-substrate and co-factor requirements for Fe(II), ascorbate, and the Krebs cycle intermediate 2-OG, and inducible changes in the cellular abundance of three closely related HIF prolyl hydroxylases (PHD1-3) provide additional interfaces with cellular oxygen status that may be important in regulating the oxygen-sensitive signal.
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PMID:Regulation of HIF: prolyl hydroxylases. 1668 27

We have shown that the proteasome is present in mammalian sperm and plays a role during fertilisation. In this work we studied the relationship between protein phosphorylation and proteasomal activity in human sperm. Aliquots of motile sperm were incubated for 0, 5 and 18 h at 37 degrees C, 5% CO2, with different concentration of the kinase inhibitors genistein, H89 or tamoxifen. Control aliquots were treated with the inhibitor solvent. The chymotrypsin-like activity of the proteasome was assayed using a fluorogenic substrate. Aliquots of spermatozoa capacitated during 18 h were incubated for 30 min with kinase inhibitors and then with 7 microM progesterone (P). The percentage of viable acrosome-reacted sperm was evaluated using FITC-labeled Pisum sativum agglutinin. The results indicate that spermatozoa treated with different concentrations of genistein and tamoxifen did not modify the chymotrypsin-like activity of the proteasome during capacitation. On the other hand, proteasome activity was significantly decreased by incubation with H89. Sperm treatment with genistein, H89 and tamoxifen significantly inhibited the P-induced acrosome reaction. Western blot analysis indicated that the proteasome inhibitor, epoxomicin, reduced serine protein phosphorylation. These results suggest that the enzymatic activity of the proteasome is modulated by protein kinase A, and that both enzymes are involved in the P-induced acrosome reaction.
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PMID:Proteasome activity and its relationship with protein phosphorylation during capacitation and acrosome reaction in human spermatozoa. 1764 68

Diphenylamine metabolism and ethylene action were evaluated as factors influencing the development of 'Braeburn' apple internal browning and cavitation during cold storage. Apples treated with the antioxidant diphenylamine (DPA) and/or the ethylene action inhibitor 1-methylcyclopropene (1-MCP) were held at 1 degrees C for up to 6 months in air or a controlled atmosphere (CA) containing 1 kPa of O2 and 3 kPa of CO2. Cortex tissues from fruit without disorders as well as from symptomatic and asymptomatic areas of fruit with disorders were analyzed for DPA and DPA derivative content. Internal browning and cavities developed in control and 1-MCP-treated fruit stored in CA, whereas air-stored and CA fruit treated with DPA or with DPA and 1-MCP prior to storage did not develop disorders. Depending on the storage regimen and duration, less DPA was detected in 1-MCP-treated fruit. The 4-hydroxydiphenylamine (4OHDPA) content of control fruit decreased during air storage duration but increased between 2 and 4 months in CA storage. 4OHDPA content in 1-MCP-treated fruit increased with storage duration in CA but not air. N-Nitrosodiphenylamine (NODPA) was detected after 2 months in control fruit stored in air or CA and in 1-MCP-treated fruit stored in CA, and NODPA content in control fruit was higher compared to that in 1-MCP-treated fruit. Accumulation of 4-methoxydiphenylamine (4MeODPA) in control fruit stored in air increased with storage duration, but 4MeODPA content did not change in 1-MCP-treated fruit stored in air or CA. 2-Nitrodiphenylamine content was reduced by prestorage treatment with 1-MCP, but storage environment and duration had no effect on its accumulation. The results indicate that CA storage increases the risk of disorder development in 'Braeburn' apples, that DPA can prevent disorder development, and that the content of DPA and DPA derivatives is influenced by storage environment and ethylene action. A clear relationship between DPA derivative formation and storage conditions that promote internal browning was not apparent.
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PMID:Diphenylamine metabolism in 'braeburn' apples stored under conditions conducive to the development of internal browning. 1838 Apr 63

The influence of four postharvest treatments, 1-methylcyclopropene (1-MCP), carbon dioxide (CO2), and nitrogen (N2), followed by fruit storage at 10 degrees C or of hydrocooling (H2O) at 1 degrees C, followed by storage at 0 degrees C on fruit quality, carotenoids, and abscisic acid (ABA) content as well as on ethylene and carbon dioxide production of "Spring Belle" peach fruits, has been examined. Ethylene production was reduced by all the treatments and raised after transfer the fruits at 20 degrees C, their ethylene production in general being lower than that of fruits continuously held at 20 degrees C. Nevertheless, 1-MCP removal enhanced the rise in ethylene occurring at 20 degrees C by the end of storage. Those changes were likely related to fruit softening but not to changes in color or in the soluble solid content (SSC). HPLC analyses showed a relative high content of xanthophylls, particularly violaxanthin. In fruits maintained in air at 20 degrees C, violaxanthin and beta-carotene contents decreased while beta-criptoxanthin increased. ABA content showed a great increase in 1-MCP and significant decrease in carbon dioxide and hydrocooling treated peaches. The results indicated hydrocooling, in combination with low temperature storage, as the best treatment maintaining fruit firmness due to the lowered respiration rate and the content of relevant carotenoids.
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PMID:Influence of postharvest treatments on quality, carotenoids, and abscisic acid content of stored "spring belle" peach (prunus persica) fruit. 1972 84


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