Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.23.17 (PCE)
 1,301 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of food on the relative bioavailability of an erythromycin particles-in-tablet formulation was studied in 27 healthy volunteers, using a four-way, crossover study design with the following treatments: one or two erythromycin capsules USP (Eryc, Parke-Davis), or one polymer-coated erythromycin particles-in-tablet (PCE, Abbott) administered fasting or with a high-fat meal. Under fasting conditions the erythromycin particles-in-tablet and erythromycin capsule formulations are bioequivalent based on similar tmax and dose-normalized Cmax and AUC values. The rate and extent of absorption from the particles-in-tablet formulation, however, are dramatically reduced following administration with a meal. Mean Cmax and AUC values decreased by 73% and 72%, respectively, and seven subjects had no detectable erythromycin plasma concentrations for 16 hours following administration of the particles-in-tablet formulation with the high-fat meal. Greater than 40% of the subjects had nonfasting Cmax and AUC values that were less than 10% of those values following administration of the dose fasting. Cmax and AUC values in nonfasting subjects were within 75% to 125% of fasting values in only two and one of 27 subjects, respectively. The erythromycin particles-in-tablet formulation therefore should not be administered with meals.
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PMID:Effect of a high-fat meal on the bioavailability of a polymer-coated erythromycin particle tablet formulation. 270 52

The clastogenic activity of tobacco smoke (TS) was established in mouse fetuses employing the micronucleus test. A 1-h exposure of pregnant mice BDF1 (C57Bl x DBA2) to TS (600 cm3 TS in a 14-l glass chamber, 4 exposures of 15 min each with 1 min intervals during which a total air change was made) on day 16/17 caused a 2-3-fold increase in the number of micronucleated polychromatic erythrocytes (MN PCEs) in fetal liver as well as in the liver of newborn mice (1-5 h after birth). A similar, although slightly greater micronucleus response occurred in fetuses obtained from pregnant mice treated repeatedly with TS (60 min/day in total) starting on day 11 of gestation. The in vivo clastogenic activity of TS was also established by evaluating the MN PCE level in the peripheral blood of newborn mice (1-5 h after birth and during the first several days of life) treated transplacentally with TS during the last third of pregnancy. The young animals (1-3 weeks old) were more sensitive to the clastogenic activity of TS as compared to their 6-month-old mothers but no data were obtained showing a possible passing of the TS-contained clastogens from 'smoking' lactating mothers to their suckling offspring. The combined application of micronucleus test proved to be very convenient and useful when studying the different aspects of TS-induced genotoxicity.
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PMID:Tobacco smoke-induced clastogenicity in mouse fetuses and in newborn mice. 271 59

Caprolactam (CAP) and benzoin (ZOIN) were tested in the mouse micronucleus test at two dose levels, one of which was the maximum tolerated dose. The compounds were administered by the oral route to groups of 5 male and 5 female mice. No statistical significant increase over control values of the frequency of PCE-containing micronuclei was observed at any dose level or sampling time, with the exception of CAP at a dose level of 700 mg/kg at the 24-h sampling time, where a small statistically significant effect was observed both when the sexes were analysed combined and separately. Due to this observation a limited repeat was carried out on CAP at the 700 mg/kg dose level at the 24-h sampling time. In the repeat study similar trends were observed even following the analysis of 5000 cells per animal. However, when these data were compared with historical control data no such effects were observed, the effects were therefore considered to be of questionable validity. Throughout the study the positive control (cyclophosphamide) gave an elevated biologically and statistically significant increase at all sampling times, thus verifying the sensitivity of the test system. It was therefore concluded that caprolactam and benzoin are not clastogenic in the mouse micronucleus test.
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PMID:An evaluation of caprolactam and benzoin in the mouse micronucleus test. 281 24

In our previous studies, we have purified a unique, paired basic residue-specific, prohormone-converting enzyme from pituitary intermediate lobe secretory vesicles. This enzyme, an aspartyl protease, was shown to cleave the intermediate lobe prohormone, pro-opiomelanocortin (POMC), to adrenocorticotropin, beta-endorphin and a 16 kDa NH2-terminal glycopeptide, in vitro [(1985) J. Biol. Chem. 260, 7194-7205]. To provide some evidence that this enzyme plays a role in prohormone conversion in the intact cell, the ability of pepstatin A, an aspartyl protease inhibitor, to block POMC processing in the mouse intermediate pituitary was investigated. By the use of a radioactive pulse-chase paradigm, [3H]POMC processing was found to be inhibited by 36.4% in pepstatin A-treated intermediate lobes. This result is consistent with the inactivation of pro-opiomelanocortin-converting enzyme by pepstatin A in the intact pituitary and further supports a role of this enzyme in POMC processing in vivo.
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PMID:The effect of pepstatin A, an inhibitor of the pro-opiomelanocortin (POMC)-converting enzyme, on POMC processing in mouse intermediate pituitary. 284 92

Pro-opiomelanocortin (adrenocorticotropin/endorphin prohormone) is processed to yield active hormones by cleavages at paired basic amino acid residues. In this study, an enzyme that specifically cleaves at the paired basic residues of this prohormone has been purified from bovine pituitary intermediate lobe secretory vesicles, the intracellular processing site of proopiomelanocortin. This enzyme, named pro-opiomelanocortin converting enzyme, has been characterized as a glycoprotein of Mr approximately 70,000. It has an apparent isoelectric point between 3.5 and 4.0. The pH optimum of the pro-opiomelanocortin converting enzyme is between 4 and 5, but the enzyme is highly active at the intravesicular pH of 5.1-5.6. The enzyme specifically cleaved the Lys-Arg pairs of pro-opiomelanocortin to yield Mr = to 21,000-23,000 ACTH, beta-lipotropin, Mr 13,000 and 4,500 ACTH, beta-endorphin, and a Mr = 16,000 NH2-terminal glycopeptide, the products synthesized by the pituitary intermediate lobe in situ. NH2- and COOH-terminal analysis of the products indicated that the pro-opiomelanocortin converting enzyme cleaves the peptide bond either between the Lys and Arg or on the carboxyl side of the Arg at Lys-Arg pairs of pro-opiomelanocortin. The intracellular localization, pH optimum, and cleavage specificity of the enzyme suggest that it may function as a pro-opiomelanocortin processing enzyme in the pituitary intermediate lobe in vivo.
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PMID:Purification and characterization of a paired basic residue-specific pro-opiomelanocortin converting enzyme from bovine pituitary intermediate lobe secretory vesicles. 298 47

The kinetics of the previously reported paired basic residue-specific pro-opiomelanocortin-converting enzyme from bovine pituitary intermediate lobe secretory vesicles (Loh, Y. P., Parish, D.C., and Tuteja, R. (1985) J. Biol. Chem. 260, 7194-7205) were studied using human 125I-beta-lipotropin as substrate. The enzyme, at a concentration of 20 ng/100 microliters cleaved human beta-lipotropin to yield gamma-lipotropin, a beta-melanotropin linked to beta-endorphin intermediate and beta-endorphin, whereas at an enzyme concentration of 40 ng/100 microliters, the substrate was completely cleaved to yield beta-endorphin and beta-melanotropin. These products were identified by their immunological properties and size on sodium dodecyl sulfate-polyacrylamide gels. The 125I-beta-endorphin product was further shown by high pressure liquid chromatography to contain two forms; the major form co-eluted with 125I-Arg0-beta h-endorphin and the minor form with 125I-beta h-endorphin. No COOH-terminal shortened forms of beta-endorphin were detected. The products formed indicate cleavages at two of the three pairs of basic residues of human beta-lipotropin, at Lys37-Lys38 and Lys57-Arg58, but not at Lys86-Lys87. The cleavage at Lys57-Arg58 occurred primarily in between these basic residues. The Km values for the cleavage of the Lys37-Lys38 and Lys57-Arg58 pairs were 1.9 and 2.5 microM, respectively. The Vmax values for the cleavage of the Lys37-Lys38 and Lys58-Arg58 pairs were 4.8 nmol/micrograms of enzyme/h and 9.1 nmol/micrograms of enzyme/h, respectively.
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PMID:Kinetic studies on the processing of human beta-lipotropin by bovine pituitary intermediate lobe pro-opiomelanocortin-converting enzyme. 301 55

The neuropeptides arginine vasopressin and oxytocin are generated from their prohormones in the hypothalamoneurohypophysial system by enzymatic cleavages at paired basic residues (i.e. Lys-Arg). This study describes the purification of an enzyme from bovine neural lobe secretory vesicles, the putative site of this processing, which is capable of cleaving several prohormones at paired basic residues. The enzyme is a glycoprotein of Mr approximately 70,000 and has an acidic pH maximum. It processes the heterologous precursors pro-opiomelanocortin and insulin at paired basic residues in a manner similar to a pro-opiomelanocortin-converting enzyme derived from bovine intermediate lobe secretory vesicles which has been described previously. In addition, the neural lobe-derived converting enzyme cleaves the human vasopressin prohormone in vitro to yield arginine vasopressin-Gly10-Lys11-Arg12 as the major vasopressin cleavage product. This indicates that the enzymatic cleavage in the vasopressin precursor occurred primarily on the carboxyl side of the arginine in the pair of Lys-Arg basic residues separating the vasopressin peptide from the neurophysin moiety in the precursor. The properties of the neural and intermediate lobe-derived enzymes are virtually identical, raising the possibility that a family of similar enzymes may be responsible for cleaving a number of prohormones at paired basic residues in different tissues.
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PMID:Purification and characterization of a paired basic residue-specific prohormone-converting enzyme from bovine pituitary neural lobe secretory vesicles. 302 39

N,N-diethylphenylacetamide (DEPA), a promising new insect repellent, was tested for mutagenicity in the in vitro Ames Salmonella/microsome mutagenicity test and the in vivo mouse micronucleus test. For the Ames test, DEPA was assayed both in the presence and absence of Aroclor 1254-induced rat-liver S-9 mix (5 and 20% S-9 fraction), using five tester strains of Salmonella typhimurium--TA97a, TA98, TA100, TA102 and TA104. For the micronucleus test, mice were exposed to DEPA through ip injection for 2 and 5 days in separate experiments, and bone marrow and peripheral blood were sampled 6 and 48 hr after the final injection, respectively. DEPA did not induce a mutagenic response in the Ames test, and mouse bone marrow and peripheral blood micronucleus tests. DEPA was not considered cytotoxic, as a depression of the percentage PCE was not observed at any dose in the range of 1 to 100 mg/kg body weight with either treatment protocol of the micronucleus test.
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PMID:N,N-diethylphenylacetamide, an insect repellent: absence of mutagenic response in the in vitro Ames test and in vivo mouse micronucleus test. 320 42

This study describes two methods for the quantitative determination of the residual fumigants ethylene dichloride (EDC), carbon tetrachloride (CCl4), trichloroethylene (TCE), ethylene dibromide (EDB) and tetrachloroethylene (PCE) in cereals (especially wheat) and other foodstuffs. In the first method, a micro steam distillation- solvent extraction apparatus is used, while the second method is based on a headspace technique. For the quantitative determination of carbon tetrachloride in cereals, the multiple headspace technique is not retained because it is too time-consuming. The analysis of the different fumigants is performed by electron-capture gas chromatography, using a fused silica capillary column, CP sil 8 CB. With the steam distillation-solvent extraction method, recoveries from 95.9% to 100.5% are obtained for the fumigants, added at two different levels. The standard deviation varies between 1.1% and 6%. Using the simple headspace technique, recoveries from 73.5% to 85.1% with a standard deviation of between 1.7% and 6.6% have been reached for the fumigants in cereals fortified at two different levels. The absolute detection limits for the five fumigants EDC, CCl4, TCE, EDB and PCE, in both methods, are 30, 0.25, 1.1, and 0.5 pg, respectively.
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PMID:Determination of fumigants in cereals and cereal products by capillary gas chromatography. 322 92

Tetrachloroethylene (perchloroethylene, PCE) is a suspected carcinogen and a common groundwater contaminant. Although PCE is highly resistant to aerobic biodegradation, it is subject to reductive dechlorination reactions in a variety of anaerobic habitats. The data presented here clearly establish that axenic cultures of Methanosarcina sp. strain DCM dechlorinate PCE to trichloroethylene and that this is a biological reaction. Growth on methanol, acetate, methylamine, and trimethylamine resulted in PCE dechlorination. The reductive dechlorination of PCE occurred only during methanogenesis, and no dechlorination was noted when CH4 production ceased. There was a clear dependence of the extent of PCE dechlorination on the amount of methanogenic substrate (methanol) consumed. The amount of trichloroethylene formed per millimole of CH4 formed remained essentially constant for a 20-fold range of methanol concentrations and for growth on acetate, methylamine, and trimethylamine. These results suggest that the reducing equivalents for PCE dechlorination are derived from CH4 biosynthesis and that the extent of chloroethylene dechlorination can be enhanced by stimulating methanogenesis. It is proposed that electrons transferred during methanogenesis are diverted to PCE by a reduced electron carrier involved in methane formation.
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PMID:Dependence of tetrachloroethylene dechlorination on methanogenic substrate consumption by Methanosarcina sp. strain DCM. 322 63


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