Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P00790 (PGA)
 2,475 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The binding of tritiated prostaglandins (PGA1, PGE1, PGF2alpha, and PGE2) to human and bovine serum albumins was studied by equilibrium dialysis and batchwise gel equilibration with Sephadex G-25. During equilibrium dialysis (36 hours, 4 degrees C), about half of the PGEs, but not PGA and PGF2alpha, were transformed into dehydration products; by contrast, equilibration of the prostaglandins was attained in less than a half-hour by the batchwise use of Sephadex G-25 at 25 degrees C, with no detectable ligand instability. The values of the apparent association constants for albumin-prostaglandin interactions were inversely related to the protein concentration in the assay systems. "True" apparent association constants (NKo) were measured by extrapolation to zero protein concentration. The NKo values were estimated to be 9.4 X 10(4), 2.7 X 10(4), 9 X 10(3) and 6 X 10(3) M-1 for the interaction of human serum albumin with PGA1, PGE1, PGF2alpha and PGE2, respectively. Very similar values were found for the corresponding bovine serum albumin-Prostaglandin interactions. When comparable, the data obtained by both methods were in excellent agreement. Our results were also in agreement with published values for PGA1 and PGF2alpha, both of which are relatively stable in neutral aqueous phase. Batchwise gel equilibration appears to be a useful method, if thermodynamically valid data are desired in the presence of possible ligand and/or "receptor" instability. We conclude that albumin binding probably affords circulating PGA1 a modest protection from its clearance mechanisms.
 ...
PMID:Prostaglandin-macromolecule interactions. I. Noncovalent binding of prostaglandins A1, E1, F2alpha, and E2 by human and bovine serum albumins. 94 73

The measurement of 13,14-dihydro-15-keto prostaglandin E2 [PGEM] is complicated by the artefactual formation of compounds of the corresponding A series which are reactive towards protein. Existing methods of assay depend on the deliberate dehydration to the 'A' form followed by cyclization in alkaline solution to a bicyclic derivative which is stable and can be measured by radioimmunoassay. We report an alternative approach using methyl oximation of the 9- and 15-keto groups which confer stability on the molecule. This derivatization is simple and does not involve an active intermediate such as those of the PGA series. The antiserum for radioimmunoassay is raised against the methyl oxime form. The label is the methyl oxime of PGEM coupled to a tripeptide Pro-gly-tyr through the nitrogen in the proline ring. This is a linkage distinct from that used to raise the antiserum and thus is not preferentially recognized over the endogenous analyte; this results in a high sensitivity assay. The results correlated well with those from the bicyclic assay when both assays were used to measure the same samples of peripheral blood from women receiving a sustained release PGE pessary for ripening the cervix. The technique provides a rapid and reliable method for determining prostaglandin E metabolites.
 ...
PMID:The measurement of the main PGE metabolite, 13,14-dihydro-15-keto prostaglandin E by radioimmunoassay using methyl oxime stabilization. 158 44

The prostaglandin (PG) content of mitogen- and antigen-stimulated leukocyte cultures was examined by a radioimmunoassay procedure empolying an antiserum reactive with PGB(1) and PGB(2), the alkaline dehydration products of PGE and PGA. At 48 h, mitogen-activated mouse spleen cell cultures showed 2-10-fold increases in the PGE, but not in the PGA, component of immunoreactive PG (iPG) fractionated by silicic acid column chromatography. Increases in iPG were detectable by h 16 in spleen cell cultures incubated with staphylococcal enterotoxin B. Since iPG levels rose only in the culture supernates and not in cells exposed to mitogens for 48 h, increases reflected extracellular release of PG. The validity of the radioimmunoassay determinations of PGE in spleen cell cultures was supported by the results of concomitant assessment of the PGE(2) content of basal and enterotoxin-stimulated cultures by gas chromatography/mass spectrometry. By the latter method, the PGE(2) content was three-fold higher in enterotoxin-activated, compared to basal, cultures at 48 h. Aspirin effectively suppressed increases in both iPG and PGE(2). In spleen cell cultures prepared from mice previously inoculated with an attenuated strain of yellow fever virus in vivo and then incubated with this virus in vitro, iPG levels increased twofold over basal at 48 h. By contrast, iPG content of spleen cell cultures prepared from saline-inoculated mice was not appreciably altered by exposure to the virus in vitro. The enhancement of iPG release from cultured spleen cells by mitogens did not correlate with an ability of these agents to increase cellular cyclic AMP (cAMP) levels. Moreover, epinephrine and cholera toxin markedly increased spleen cell cAMP content but had no demonstrable effect on basal iPG levels, suggesting iPG release from these cells was not mediated by cAMP. Incubation with mitogens also enhanced the iPG content of 72-cultures of human peripheral leukocytes and of human lymphocytes isolated by nylon chromatography. However, the iPG of cultures of human lymphocytes purified by glass bead chromatography and of mouse thymocytes was not appreciably altered when these cells were cultured with mitogens, even though DNA synthesis in both instances was markedly increased. Accordingly, iPG release was not an invariable concomitant of increased DNA synthesis in lymphoid cell cultures. In summary, the results demonstrate that mitogen and antigen stimulation of leukocytes in culture may be accompanied by enhanced release of PGE. The mechanisms mediating this phenomenon and its biologic significance remain to be delineated, but participation of PGE in immunologically induced inflammatory responses seems possible.
 ...
PMID:Release of prostaglandin by mitogen- and antigen-stimulated leukocytes in culture. 436 90

The ultraviolet (UV) and optical rotatory dispersion (ORD) spectra of prostaglandins E(1), A(1), B(1), and their naturally derived 15-epimers are presented. The dehydration sequence E --> A --> B under acidic and basic conditions has been studied by UV and ORD. Conditions for quantitative conversion of PGE(1) to PGA(1) are described. The combination of ORD and UV affords a nondestructive assay which can determine the relative amounts of E-, A-, and B-type prostaglandins with as little as 1-2 micro g of material. The total quantity of prostaglandins can be estimated (+/-15%) in this way or, more accurately, by treatment with alkali of an aliquot (200 ng is sufficient) and determination of the change in absorbance at 278 nm.
 ...
PMID:Dehydration of prostaglandins: study by spectroscopic method. 578 3

Spectroscopic and kinetic methods have been used to explore the roles of divalent metal ions in the enolase-catalyzed dehydration of 2-phosphoglycerate (2-PGA). Enolase requires 2 equiv of metal ion per active site for maximal activity. Previous crystallographic studies [Larsen, T. M., Wedekind, J. E., Rayment, I., and Reed, G. H. (1996) Biochemistry 35, 4349-4358] showed that both magnesium ions coordinated to the carboxylate group of the substrate/product-a scheme consistent with metal ion assistance in formation of the enolate intermediate. Electron paramagnetic resonance (EPR) data with 17O-labeled forms of phosphoenolpyruvate show that Mn(2+), bound at the lower affinity site, coordinates to one carboxylate oxygen and one phosphate oxygen of the substrate. These observations are fully consistent with the crystallographic data. Plots of activity versus log [metal ion] are bell-shaped, and the inhibitory phases of the profiles have been previously attributed to binding of metal ions at ancillary sites on the enzyme. However, the activation profiles and measurements of 2H kinetic isotope effects support an ordered kinetic mechanism wherein binding of 2-PGA precedes binding of the second metal ion, and release of the second metal ion occurs prior to departure of phosphoenolpyruvate. High concentrations of metal ion lead to inhibition in the ordered mechanism by interfering with product release. The 2H kinetic isotope effect is diminished in the inhibitory phases of the metal ion activation profiles in a manner that is consistent with the predominantly ordered mechanism. Zn(2+) gives lower maximal activity than Mg(2+), apparently due to slow release of Zn(2+) from the product complex. Addition of imidazole increases the maximal rate apparently by accelerating the release of Zn(2+) from the enzyme.
 ...
PMID:Role of metal ions in catalysis by enolase: an ordered kinetic mechanism for a single substrate enzyme. 1143 70

Mediators of cholera toxin (CT)-induced fluid secretion include 3',5'-adenosine monophosphate (cAMP), prostaglandin E(2) (PGE(2)), and 5-hydroxytryptamine (5-HT). Administration of L-histidine significantly reduced the net secretory response of the small intestine of mice challenged with CT and reduced the capacity of PGE(2) to stimulate Na+ transport in Ussing chambers. We demonstrated that L-histidine chemically modified the structure of PGE(2) but had no direct effect on cAMP or 5-HT. L-Histidine and imidazole reacted with PGE(2) in vitro in cell-free mixtures incubated at 37 degrees C and pH 7.0 under an atmosphere of N(2) with the formation of PGE(2)-imidazole and PGE(2)-histidine covalent adducts. Nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) analysis of the purified adduct showed that imidazole catalyzed the dehydration of PGE(2). A Michael adduct then was formed between C11 of 11-deoxy-Delta(10) PGE(2) (PGA(2)) and the tau nitrogen in the imidazole ring of L-histidine. Importantly, the isolated PGE(2)-imidazole and PGE(2)-histidine adducts inhibited CT-induced fluid loss and cAMP accumulation in mouse intestinal loops. The protection provided by PGE(2)-imidazole, PGE(2)-histidine, and L-histidine against intestinal fluid loss could provide a basis for future therapy against cholera.
 ...
PMID:Cholera toxin-induced PGE(2) activity is reduced by chemical reaction with L-histidine. 1147 60

Cyclopentenone prostaglandins (cyPGs) are produced by dehydration of precursor molecules. The cyPGs are reported to have proapoptotic effects in a variety of cell types. However, cyPGs, particularly 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), can also exert cytoprotective effects at relatively low concentrations. The cytoprotective activity of cyPGs appears to be mediated by the reactive alpha,beta-unsaturated carbonyl group located in the cyclopentene ring. In this study, we investigated the effect of cyPGs on the expression of heme oxygenase-1 (HO-1), a ubiquitous stress-responsive enzyme that catalyzes oxidative cleavage of heme to form iron, carbon monoxide, and biliverdin. Treatment of the human breast cancer cell line (MCF-7) with 15d-PGJ(2) resulted in a concentration- and time-dependent increase in the expression of HO-1, whereas prostaglandin A(2) (PGA(2)) and the non-PG derivative 2-cyclopenten-1-one failed to induce HO-1 expression at the protein level. RT-PCR revealed that the expression of HO-1 mRNA was induced at 6 h by 15d-PGJ(2) at 10 microM. However, PGA(2) induced HO-1 mRNA expression at a higher concentration (30 microM). 2-Cyclopenten-1-one did not induce the expression of HO-1 mRNA at all. Likewise, 15d-PGJ(2) treatment for 6 h led to phosphorylation of Akt/protein kinase B (PKB) to a greater extent than that achieved with PGA(2). Thus, the induction of HO-1 expression and the activation of Akt/PKB by 15d-PGJ(2) and PGA(2) are likely to confer cytoprotective or antiapoptotic effects exerted by these cyPGs.
 ...
PMID:Effects of cyclopentenone prostaglandins on the expression of heme oxygenase-1 in MCF-7 cells. 1565 34

Chloroplasts, isolated from protoplasts of the green alga, Chlorella ellipsoidea, were estimated to be 99% intact by the ferricyanide-reduction assay, and gave CO(2) and PGA-dependent rates of O(2) evolution of 64.5 to 150 micromoles per milligram of chlorophyll per hour, that is 30 to 70% of the photosynthetic activity of the parent cells. Intact chloroplasts showed no carbonic anhydrase activity, but it was detected in preparations of ruptured organelles. Rates of photosynthesis, measured in a closed system at pH 7.5, were twice the calculated rate of CO(2) supply from the uncatalyzed dehydration of HCO(3) (-) indicating a direct uptake of bicarbonate by the intact chloroplasts. Mass spectrometric measurements of CO(2) depletion from the medium on the illumination of chloroplasts indicate the lack of an active CO(2) transport across the chloroplast envelope.
 ...
PMID:Uptake of Inorganic Carbon by Isolated Chloroplasts of the Unicellular Green Alga Chlorella ellipsoidea. 1666 62

A LC-MS/MS method has been developed to analyze tetranor PGE-M, the major urinary metabolite of PGE(2), that involves the acid-catalyzed dehydration of tetranor PGE-M and its deuterated (d(6)) analog followed by LC-MS/MS measurement of the dehydrated tetranor PGE-M product (tetranor PGA-M). We also report a method for quantification of creatinine in urine by LC-MS/MS to normalize tetranor PGE-M concentrations with that of urinary creatinine. These methods were used to study the effect of aspirin on urinary tetranor PGE-M levels in healthy male volunteers. Aspirin did not affect urinary creatinine concentrations but decreased urinary tetranor PGE-M concentrations by approximately 44%.
 ...
PMID:Liquid chromatography-tandem mass spectrometric quantification of the dehydration product of tetranor PGE-M, the major urinary metabolite of prostaglandin E(2) in human urine. 1863 14

Prostaglandins (PG) are known to induce pain perception indirectly by sensitizing nociceptors. Accordingly, the analgesic action of nonsteroidal anti-inflammatory drugs (NSAIDs) results from inhibition of cyclooxygenases and blockade of PG biosynthesis. Cyclopentenone PGs, 15-d-PGJ(2), PGA(2), and PGA(1), formed by dehydration of their respective parent PGs, PGD(2), PGE(2), and PGE(1), possess a highly reactive alpha,beta-unsaturated carbonyl group that has been proposed to gate the irritant transient receptor potential A1 (TRPA1) channel. Here, by using TRPA1 wild-type (TRPA1(+/+)) or deficient (TRPA1(-/-)) mice, we show that cyclopentenone PGs produce pain by direct stimulation of nociceptors via TRPA1 activation. Cyclopentenone PGs caused a robust calcium response in dorsal root ganglion (DRG) neurons of TRPA1(+/+), but not of TRPA1(-/-) mice, and a calcium-dependent release of sensory neuropeptides from the rat dorsal spinal cord. Intraplantar injection of cyclopentenone PGs stimulated c-fos expression in spinal neurons of the dorsal horn and evoked an instantaneous, robust, and transient nociceptive response in TRPA1(+/+) but not in TRPA1(-/-) mice. The classical proalgesic PG, PGE(2), caused a slight calcium response in DRG neurons, increased c-fos expression in spinal neurons, and induced a delayed and sustained nociceptive response in both TRPA1(+/+) and TRPA1(-/-) mice. These results expand the mechanism of NSAID analgesia from blockade of indirect nociceptor sensitization by classical PGs to inhibition of direct TRPA1-dependent nociceptor activation by cyclopentenone PGs. Thus, TRPA1 antagonism may contribute to suppress pain evoked by PG metabolites without the adverse effects of inhibiting cyclooxygenases.
 ...
PMID:Cox-dependent fatty acid metabolites cause pain through activation of the irritant receptor TRPA1. 1868 86


1 2 Next >>