Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.69 (APC)
 16,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The anticancer drug CPT-11 (7-ethyl-[4(1-piperidino)-1-piperidino]carbonyloxycamptothecin) is a water-soluble derivative of camptothecin. We report here the conversion of APC (7-ethyl-[4-N-(5-aminopentanoic acid)-1-piperidino] carbonyloxycamptothecin), an inactive metabolite of CPT-11, to SN-38 (7-ethyl-10-hydroxycamptothecin), the active metabolite of CPT-11, by a rabbit liver carboxylesterase. This reaction is not catalyzed by any known human enzyme. The formation of SN-38 from APC was characterized by an apparent Km of 37.9 +/- 7.1 microM and a Vmax of 16.9 +/- 0.9 pmol/units/min. SN-38 was confirmed as a reaction product by high-performance liquid chromatography and mass spectrometry. A 24-h incubation of 10 microM APC with 500 units/ml of rabbit carboxylesterase produced 4 microM SN-38. The product of this reaction inhibited the growth of U373 MG human glioblastoma cells in vitro. The IC50 for a 24-h exposure of U373 MG cells to APC in the presence of 50 units/ml of rabbit carboxylesterase was 0.27 +/- 0.08 microM, whereas APC alone demonstrated no inhibition of growth at concentrations up to 1 microM. The IC50 of U373 MG cells transfected with the cDNA encoding the rabbit carboxylesterase (U373pIRESrabbit) and exposed to APC for 24 h was 0.8 +/- 0.1 microM APC, whereas the growth of cells transfected with vector control (U373pIRES) was unaffected by up to 1 microM APC. Because APC is nontoxic to human cells, we are investigating the possibility of using APC/rabbit carboxylesterase in a prodrug/enzyme therapeutic approach.
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PMID:Conversion of the CPT-11 metabolite APC to SN-38 by rabbit liver carboxylesterase. 986 25

Iceland is a major producer of cold water shrimp, Pandalus borealis. In recent years considerable attention has been given to improve hygiene in the factories producing cooked, peeled and frozen shrimp. To keep track of the bacteriological status of the end product, shrimp from most of the factories is routinely analysed bacteriologically by the request of shrimp exporters. This paper reports on the results of a bacteriological analysis of 7913 samples of shrimp from 26 Icelandic factories over a 6-year period. The results showed that the geometric mean of APC (at 35 degrees C) was 1718 per g and 57% of the samples had APC under 1000 per g. Some 70% of the samples had less than one coliform per g and 99.9% of the samples had less than one faecal coliform per g. Staphylococcus aureus was detected in less than 0.2% of the samples. The results show improvement in bacterial profiles, mainly total coliforms, over the 6-year period. Overall, the results show acceptable bacterial numbers in the finished product, indicating a high level of hygiene. Listeria spp. were, however, found in 270 of 3331 samples examined or 8.1%. Species identification was done on 49 of the 270 positive samples. The proportion of L. monocytogenes was found to be 26.5%.
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PMID:Microbiological quality of Icelandic cooked-peeled shrimp (Pandalus borealis). 992 47

Lung surfactant films at the air/water interface exhibit the particularity that surfactant molecules are expelled from the surface monolayer into a surface associated multilamellar phase during compression. They are able to re-enter the surface film during the following expansion. The underlying mechanism for this behavior is not fully understood yet. However, an important role is ascribed to the surfactant-associated protein C (SP-C). Here, we studied a model lung surfactant, consisting of dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylglycerol (DPPG), and SP-C, by means of scanning near-field optical microscopy (SNOM). Attaching a fluorescent dye to the protein allowed the localization of its lateral distribution at various surface pressures with high resolution. At an early stage of compression, the film appears demixed into a pure lipid phase and a protein-enriched phase. Within the latter phase, protein aggregations are revealed. They show a uniform density, having three times the fluorescence intensity of their surroundings. Across the phase boundary between the lipid phase and the protein-rich phase, there is a protein density gradient rather than an abrupt border. When the film is highly compressed, we observe the formation of multilamellar structures that are fluorescent. They are often surrounded by a slightly fluorescent monolayer. The fluorescence of the multilayer stacks (i. e., the protein content per unit area) is proportional to the height of the stacks.
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PMID:Distribution of the surfactant-associated protein C within a lung surfactant model film investigated by near-field optical microscopy. 1062 Mar 9

Genetic knockout or pharmacological inhibition of cyclooxygenase-2 decreases the number and size of adenomas in mouse models of familial adenomatous polyposis. Epidemiological and clinical studies in humans indicate that the entire class of nonsteroidal anti-inflammatory drugs (NSAIDs) that inhibit both COX-1 and COX-2 enzymes are promising colon cancer chemopreventive agents. We used the Apc mutant Min mouse model to test combinations of agents that might maximize preventive benefit with minimal toxicity because they act via different mechanisms. Min mice (n = 144) were exposed to low doses of the nonselective COX inhibitor piroxicam and the ornithine decarboxylase (ODC) inhibitor difluoromethylornithine (DFMO), beginning at the time they were weaned and continuing throughout the duration of the experiment. Piroxicam at 12, 25, and 50 ppm in the diet caused dose-dependent decreases in the number of tumors in the middle and distal portions of the small intestine. This decrease in tumor multiplicity was associated with a striking decrease in the size of those tumors that did grow out. In contrast, none of the doses of piroxicam alone decreased tumor multiplicity in the proximal portion of the intestine (duodenum). Exposure to DFMO (0.5 or 1.0% in water) caused a dose-dependent decrease in tumor multiplicity in the middle and distal portions of the small intestine. However, this decreased multiplicity was not associated with a striking decrease in the size of the tumors. Combined treatment of mice with piroxicam plus DFMO was much more effective than either agent alone and resulted in a significant number of mice totally free of any intestinal adenomas (P < 0.001), in contrast to the 100% incidence and high multiplicity in control Min mice. In addition to this profound effectiveness in reducing tumor number, the few residual tumors in mice treated with the combined drugs were markedly smaller in size than tumors that arose from control Min mice. These experiments suggest that selective COX-2 inhibition combined with ODC inhibition is a very promising approach for colon cancer prevention. These COX-2 and ODC inhibitor drugs were not overtly toxic at the doses used when administered to mice after weaning. However, when treatment was begun in utero, the Mendelian expected progeny ratio of 1:1 that we routinely obtained in untreated control litters was no longer observed. Apc(min)/+ progeny of pregnant dams treated with piroxicam and/or DFMO were reduced in number and their ratio to Apc+/+ progeny was decreased to approximately 0.28:1. Thus, these agents are effective against adenomas that have homozygous mutation of the APC gene and also select against fetuses bearing a heterozygous mutation in the APC gene.
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PMID:Chemopreventive efficacy of combined piroxicam and difluoromethylornithine treatment of Apc mutant Min mouse adenomas, and selective toxicity against Apc mutant embryos. 1076 73

New amphiphilic photochromic benzo-15(18)-crown-5(6) ethers (APC) differing in the position of the octadecyl substituent and the size of the crown cavity were synthesized. The compounds form stable monolayers in the air/water and air/alkaline metal salt solution interfaces. The results of the pressure isotherm measurements, atomic force microscopy (AFM), and electronic spectroscopy show that the structure of the monolayers formed depends on the structure of the parent APC and the nature of the cation in salt solutions. The area per molecule of APC in the monolayer (specific area) is the smallest on the water surface and increases by 20-40% on the aqueous subphase surface with an increasing concentration of salts therein to indicate the formation of APC complexes with the metal cations. When the hydrophobic aliphatic substituent is displaced from position 3 to position 5 of the benzothiazole ring, the specific area on the surface of water and subphases decreases twofold, which indicates the compactization of the monolayer on this modification. A reversible E-Z-photoisomerization of APC was found in the monolayers formed in the salt solution/air interface. The features of the reaction are defined by the specific organization of the amphiphilic molecules in the monolayer and by the nature of the cation.
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PMID:[Synthesis of amphiphilic photochromic benzo-15(18)-crown-5(6)-ethers and their properties in monolayers]. 1103 31

A multiple-hurdle antimicrobial process for beef trim was developed. The microbial profiles of inoculated lean beef trim tissue (BTL) and fat-covered lean beef trim (BTF) were monitored during prolonged refrigerated storage following the application of successive multiple antimicrobial treatments applied to inoculated beef trim on a processing conveyor belt set at a belt speed of 1 cm/s. Beef trim (meat size approximately 15 by 15 cm) was preinoculated with bovine feces before all treatments that included the following: control, no treatment; water wash at 65 psi for five passes; water plus lactic acid (2% [vol/vol] room temperature lactic acid wash at 30 psi for three passes); combination treatment 1 (water plus 65 degrees C hot water at 30 psi for one pass plus hot air at 510 degrees C for four passes plus lactic acid), combination treatment 2 (water plus hot water at 82 degrees C for one pass plus hot air at 510 degrees C for five passes plus lactic acid), and combination treatment 3 (water plus hot water at 82 degrees C for three passes plus hot air at 510 degrees C for six passes plus lactic acid). The effects of treatments on bacterial populations were monitored by enumerating mesophilic aerobic bacteria (APC), presumptive lactic acid bacteria (PLAB), psychrotrophic bacteria (PCT), coliforms, and Escherichia coli biotype 1 on product stored for up to 7 days at 4 degrees C. In the case of BTL, the numbers of APC, PCT, and PLAB increased during storage at 5 degrees C, whereas the numbers of coliform and E. coli decreased on average by 1.8 log CFU/cm2, then remained constant following the initial reduction. Negligible effects on color quality were observed from multihurdle treatment combination 1. In the case of the BTF, the microbial reductions by treatments were much greater than the reduction on BTL. The pH of treated BTF increased more slowly than the pH of treated BTL, resulting in further reduction of the microflora on BTF. Except for control and water treatments, all sample treatments involving lactic acid resulted in continuously decreasing microbial populations. Based on microbial reduction and quality aspects, it was concluded that successively applied combination antimicrobial treatments for meat trim could offer potential food safety benefits.
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PMID:Development of a multiple-step process for the microbial decontamination of beef trim. 1119 43

C-Terminal binding protein (CtBP) interacts with a highly conserved amino acid motif (PXDLS) at the C terminus of adenovirus early region 1A (AdE1A) protein. This amino acid sequence has recently been demonstrated in the mammalian protein C-terminal interacting protein (CtIP) and a number of Drosophila repressors including Snail, Knirps and Hairy. In the study described here we have examined the structures of synthetic peptides identical to the CtBP binding sites on these proteins using NMR spectroscopy. It has been shown that peptides identical to the CtBP binding site in CtIP and at the N terminus of Snail form a series of beta-turns similar to those seen in AdE1A. The PXDLS motif towards the C terminus of Snail forms an alpha-helix. However, the motifs in Knirps and Hairy did not adopt well-defined structures in TFE/water mixtures as shown by the absence of medium range NOEs and a high proportion of signal overlap. The affinities of peptides for Drosophila and mammalian CtBP were compared using enzyme-linked immunosorbent assay. CtIP, Snail (N-terminal peptide) and Knirps peptides all bind to mammalian CtBP with high affinity (K(i) of 1.04, 1.34 and 0.52 microM, respectively). However, different effects were observed with dCtBP, most notably the affinity for the Snail (N-terminal peptide) and Knirps peptides were markedly reduced (K(i) of 332 and 56 microM, respectively) whilst the Hairy peptide bound much more strongly (K(i) for dCtBP of 6.22 compared to 133 microM for hCtBP). In addition we have shown that peptides containing identical PXDLS motifs but with different N and C terminal sequences have appreciably different affinities for mammalian CtBP and different structures in solution. We conclude that the factors governing the interactions of CtBPs with partner proteins are more complex than simple possession of the PXDLS motif. In particular the overall secondary structures and amino acid side chains in the binding sites of partner proteins are of importance as well as possible global structural effects in both members of the complex. These data are considered evidence for a multiplicity of CtBPs and partner proteins in the cell.
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PMID:Structural determinants outside the PXDLS sequence affect the interaction of adenovirus E1A, C-terminal interacting protein and Drosophila repressors with C-terminal binding protein. 1125 8

Na+ binding to thrombin enhances the catalytic activity toward numerous synthetic and natural substrates. The bound Na+ is located in a solvent channel 16 A away from the catalytic triad, and connects with D189 in the S1 site through an intervening water molecule. Molecular modeling indicates that the G184K substitution in thrombin positions the protonated epsilon-amino group of the Lys side-chain to replace the bound Na+. Likewise, the G184R substitution positions the guanidinium group of the longer Arg side-chain to replace both the bound Na+ and the connecting water molecule to D189. We explored whether the G184K or G184R substitution would replace the bound Na+ and yield a thrombin derivative stabilized in the highly active fast form. Both the G184K and G184R mutants lost sensitivity to monovalent cations, as expected, but their activity toward a chromogenic substrate was compromised up to 200-fold as a result of impaired diffusion into the S1 site and decreased deacylation rate. Interestingly, both G184K and G184R substitutions compromised cleavage of procoagulant substrates fibrinogen and PAR1 more than that of the anticoagulant substrate protein C. These findings demonstrate that Na+ binding to thrombin is difficult to mimic functionally with residue side-chains, in analogy with results from other systems.
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PMID:Replacement of thrombin residue G184 with Lys or Arg fails to mimic Na+ binding. 1128 81

To study the structure-function relationship of pulmonary surfactant under conditions close to nature, molecular films of a model system consisting of dipalmitoylphosphatidylcholine, dipalmitoylphosphatidylglycerol, and surfactant-associated protein C were prepared at the air-water interface of air bubbles about the size of human alveoli (diameter of 100 microm). The high mechanical stability as well as the absence of substantial film flow, inherent to small air bubbles, allowed for scanning force microscopy (SFM) directly at the air-water interface. The SFM topographical structure was correlated to the local distribution of fluorescent-labeled dipalmitoylphosphatidylcholine, as revealed from fluorescence light microscopy of the same bubbles. Although SFM has proven before to be exceptionally well suited to probe the structure of molecular films of pulmonary surfactant, the films so far had to be transferred onto a solid support from the air-water interface of a film balance, where they had been formed. This made them prone to artifacts imposed by the transfer. Moreover, the supported monolayers disallowed the direct observation of the structural dynamics associated with expansion and compression of the films as upon breathing. The current findings are compared in this respect to our earlier findings from films, transferred onto a solid support.
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PMID:Scanning force microscopy at the air-water interface of an air bubble coated with pulmonary surfactant. 1175 34

Irinotecan (CPT-11), a water-soluble topoisomerase I inhibitor, is metabolized by carboxylesterase enzymes to form an active metabolite, SN-38. Recent studies have shown that irinotecan also undergoes oxidative metabolism by the P450 isozyme CYP3A4, leading to the formation of a minor inactive metabolite, 7-ethyl-10-[4-N-[(5-aminopentanoic acid)-1-piperidino]-carbonyloxy-camptothecin (APC). The elucidation of this metabolic pathway suggests the potential for drug interactions when irinotecan is administered with other inducers or substrates of CYP3A4. In this report, the authors summarize the pharmacokinetic profile of irinotecan and its major metabolites with and without concomitant phenytoin administration in an individual patient. These studies revealed that concomitant phenytoin administration resulted in a marked decrease in the systemic exposure to irinotecan and SN-38 and an increase in the exposure to APC. The area under the curve of irinotecan and SN-38 decreased by 63% and 60%, respectively; the area under the curve of APC increased by approximately 16%. Further detailed pharmacokinetic studies of irinotecan in patients receiving concomitant therapy with enzyme-inducing anticonvulsants are required so that rational dosing recommendations can be provided for this patient population.
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PMID:Influence of phenytoin on the disposition of irinotecan: a case report. 1199 Jun 99


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