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

---

Query: EC:4.1.1.17 (ornithine decarboxylase)
6,351 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The biodegradative ornithine decarboxylase of Escherichia coli has been purified to apparent homogeneity. At its pH optimum (pH 7.0), the enzyme exists as a dimer of 160,000 molecular weight. Aggregation of the dimer was promoted by lower pH values. The enzyme requires pyridoxal 5'-phosphate for activity. The coenzyme appears to be bound in Schiff base linkage as suggested by spectral studies and inhibition by NaBH4. The following sequence was determined for the coenzyme binding site: Val-His-(epsilon-Pxy)Lys-Gln-Gln-Ala-Gly-Gln. The properties of this enzyme are compared with the other biodegradative amino acid decarboxylases that have been isolated from E. coli.
...
PMID:Biodegradative ornithine decarboxylase of Escherichia coli. Purification, properties, and pyridoxal 5'-phosphate binding site. 24 Mar 88

The effect of daily treatment with the pure antiandrogen Flutamide has been studied either alone or in combination with the LHRH agonist [D-Trp6, des-Gly-NH2(10)]LHRH ethylamide (LHRH-A), on testicular and prostatic functions in adult male rats. Treatment for 10 days with Flutamide (5 mg/rat, twice daily) caused a marked stimulation of plasma testosterone (T) associated with a significant increase in plasma gonadotropin concentrations and inhibited plasma PRL levels. Testicular weight is not changed following antiandrogen administration but testicular LH/hCG receptor levels are markedly decreased with no change in FSH receptor levels. Moreover, Flutamide treatment alone produces an important inhibition of ventral prostate and seminal vesicle weights associated with a significant decrease in prostatic beta-adrenergic receptor levels but no change is observed in specific ornithine decarboxylase (ODC) activity. Daily LHRH-A treatment at the dose of 1 microgram/day for 10 days decreases plasma T to levels comparable to those found in orchiectomized men (0.30 +/- 0.5 ng/ml). This effect is associated with an almost complete loss of testicular LH/hCG receptors, a decrease in testicular weight, a significant increase in plasma gonadotropins and a marked inhibition of plasma PRL concentration. A relatively smaller inhibition of ventral prostate and seminal vesicle weights follows treatment with the LHRH agonist alone, this effect being accompanied by a significant reduction in beta-adrenergic receptor concentration but no change in prostatic ODC activity. Combination of the two drugs, however, caused a potent inhibitory effect on both ventral prostate and seminal vesicle weight to values similar to those found in castrated rats. The prostatic weight loss is accompanied by a marked fall in ODC activity and in the concentration of beta-adrenergic receptors. The present data clearly show that combined treatment with an LHRH agonist and a pure antiandrogen is highly effective in inhibiting, not only prostatic growth, but also two androgen-sensitive parameters of prostatic activity.
...
PMID:Characteristics of flutamide action on prostatic and testicular functions in the rat. 283 89

Refeeding fasted rats with normal rat food and with a variety of amino acids increases ornithine decarboxylase (ODC) activity considerably. The time course of that increase, the areas of the digestive tract directly affected, and the effective concentrations of stimulants are unknown. By use of isolated 5-cm segments of rat jejunum, we determined that maximal activation of ODC occurred after a 2-h exposure to 0.6 M glycine. Increased activity was first apparent after a 1-h exposure to glycine and was significant after a 2-h exposure to 0.05 M glycine. ODC activity increased the most in segments of jejunum, followed by segments of ileum and then duodenum. Glycine (0.4 M) failed to increase ODC activity in gastric and colonic mucosa. Interestingly, D-alanine was more effective than L-alanine in stimulating ODC activity in the jejunum. Enzyme activity was not dependent on osmotic activity of the test substances. Glucose increased enzyme activity, but mannitol and fructose were without effect. The effects of glycine were significantly greater than those of glucose. In summary, ODC of the small intestinal mucosa is increased by direct contact with amino acids and glucose within 2 h after exposure. Increased enzyme activity depends on the nature of the stimulant rather than the osmotic activity of the solution in contact with the mucosa.
...
PMID:Stimulation of ornithine decarboxylase activity in digestive tract mucosa. 363 Dec 67

The responses of male noninbred rat colonic epithelial ornithine decarboxylase (EC 4.1.1.17) (ODC) and S-adenosyl-L-methionine decarboxylase (EC 4.1.1.50) (SAMD) activities following topical administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or bile salts were studied. A single intrarectal installation of 13 mumol of MNNG resulted in a significant (p < 0.001) 20-fold peak ODC activity after 4 hr, with a prompt return to control levels by 12 hr. Stimulation of SAMD activity was less pronounced but significant (p < 0.01), with a broad 2-fold peak over controls. No significant responses of colonic epithelial enzyme activities were detected following a single intrarectal instillation of N-methyl-N'-nitroguanidine, a noncarcinogenic and nonmutagenic metabolite of MNNG, at a dose equimolar to that of MNNG. Bile salts significantly (p < 0.001) induced ODC with almost the same kinetic pattern as that observed after MNNG administration in the following order: sodium deoxycholate > sodium chenodeoxycholate > sodium cholate. Activations of SAMD were similar for these 3 bile salts. Glycine- or taurine-conjugated deoxycholate showed ODC and SAMD enzyme activations similar to that of nonconjugated deoxycholate. No significant enzyme response was seen after sodium dehydrocholate treatment. Stimulation of activities of both enzymes was directly dependent on bile salt dose. Induced ODC and SAMD activities were principally localized in colonic epithelium. Deoxycholate-stimulated enzyme activities were significantly inhibited by cycloheximide. Enzyme stimulations by active compounds were accompanied by morphological changes such as mucosal cell degeneration, mucus depletion, submucosal congestion, and punctate hemorrhage, followed by submucosal leukocytic cellular infiltration. These data support the concept that initiating and promoting events may be involved in colon carcinogenesis.
...
PMID:Early induction of rat colonic epithelial ornithine and S-adenosyl-L-methionine decarboxylase activities by N-methyl-N'-nitro-N-nitrosoguanidine or bile salts. 744 10

The aim of this study was to investigate the effect of cell spreading on the induction of ornithine decarboxylase and the rate of putrescine uptake in anchorage-dependent and anchorage-independent cells. Plating non-transformed IEC-6 epithelial cells at high versus low cell density restricted cell spreading from 900 microns 2 to approximately 140 microns 2, blunted the transient induction of ornithine decarboxylase activity from 202 to 32 pmol 14CO2/mg protein per hour and reduced the rate of [14C] putrescine uptake from 46 to 23 pmol/10(5) cells per hour. The mean spreading area of the cell population was controlled by coating tissue culture dishes with the nonadhesive polymer, polyHEMA. Ornithine decarboxylase activity and putrescine uptake correlated with cell spreading with minimal spreading (263 microns 2) corresponding to an 83% decrease in ornithine decarboxylase activity and 51% decrease in the rate of putrescine uptake. Adding the RGD peptide, Gly-Arg-Gly-Glu-Ser-Pro to the medium of sparsely plated cells resulted in rapid reductions in cell spreading concomitant with dose-dependent decreases in ornithine decarboxylase activity and putrescine uptake. Finally, minimizing cell spreading by depriving cells of substratum contact completely abolished serum-induced increases in ornithine decarboxylase and reduced the rate of putrescine uptake by 47%. In contrast to IEC-6 cells, ornithine decarboxylase of neoplastic HTC-116 cells was constitutively expressed with basal and stimulated activity (193 and 982 pmol 14CO2/mg protein per hour, respectively) completely independent of cell adhesion. Putrescine uptake, however, was abolished in the absence of cell adhesion. These data suggest that the induction of ornithine decarboxylase activity and the rate of putrescine uptake correlate with spreading of anchorage-dependent IEC-6 cells and that ornithine decarboxylase activity but not putrescine uptake, appears to be independent of spreading of neoplastic HTC-116 cells.
...
PMID:Cell spreading and the regulation of ornithine decarboxylase. 871 85

The pyridoxal 5'-phosphate (PLP) binding site in Trypanosoma brucei ornithine decarboxylase (ODC) has been studied by site-directed mutagenesis and spectroscopy. The beta/alpha barrel model proposed for the eukaryotic ODC structure predicts that the phosphate group of PLP is stabilized by interactions with a Gly-rich loop (residues 235-237) and by a salt bridge to Arg-277 [Grishin, N. V., Phillips, M. A., & Goldsmith, E. J. (1995) Protein Sci. 4, 1291-1304]. Mutation of Arg-277 to Ala increases the K(m) for PLP by 270-fold compared to that of wild-type ODC while reducing k(cat) by only 2-fold at pH 8. PLP binding affinity was measured directly by ultrafiltration; the K(d) for PLP is at least 20-fold higher in the mutant enzyme at pH 8. In addition, R277A ODC also has weaker binding affinities for a series of cofactor analogs than the wild-type enzyme. These results demonstrate that Arg-277 is necessary for high-affinity PLP binding by ODC. The 31P NMR spectra of ODC suggest that the phosphate is bound in a strained conformation as a dianion to both wild-type and R277A ODC. However, the 31P chemical shift for R277A ODC (6.7 ppm) is 0.5 ppm downfield from that observed for the wild-type enzyme, indicating that the environment of the enzyme-bound phosphate is altered in the mutant enzyme. The binding affinity of PLP for both wild-type and R277A ODC is weaker at high pH, corresponding to the titration of a protonated species with a pK(a) of approximately 8.5. Concomitant with these changes are a decreased k(cat) and an altered absorption spectra which arises from bound PLP. PLP bound to wild-type ODC has a 31P chemical shift and a CD signal observable over the entire tested pH range (7-9). In contrast, for R277A ODC between pH 8 and 9, the 31P chemical shift becomes solution-like and the CD signal is abolished. The data suggest that for R277A ODC the rigid PLP binding mode which characterizes the wild-type enzyme is lost at high pH. Thus, multiple interactions between the wild-type active site and PLP maintain the cofactor in a constrained conformation that is essential for efficient catalysis, tempering the consequence of the removal of any single interaction.
...
PMID:Role of Arg-277 in the binding of pyridoxal 5'-phosphate to Trypanosoma brucei ornithine decarboxylase. 910 65

Ornithine decarboxylase (ODC) is a pyridoxal 5'-phosphate (PLP) dependent homodimeric enzyme. It is a recognized drug target against African sleeping sickness, caused by Trypanosoma brucei. One of the currently used drugs, alpha-difluoromethylornithine (DFMO), is a suicide inhibitor of ODC. The structure of the T. brucei ODC (TbODC) mutant K69A bound to DFMO has been determined by X-ray crystallography to 2.0 A resolution. The protein crystallizes in the space group P2(1) (a = 66.8 A, b = 154.5 A, c = 77.1 A, beta = 90.58 degrees ), with two dimers per asymmetric unit. The initial phasing was done by molecular replacement with the mouse ODC structure. The structure of wild-type uncomplexed TbODC was also determined to 2.9 A resolution by molecular replacement using the TbODC DFMO-bound structure as the search model. The N-terminal domain of ODC is a beta/alpha-barrel, and the C-terminal domain of ODC is a modified Greek key beta-barrel. In comparison to structurally related alanine racemase, the two domains are rotated 27 degrees relative to each other. In addition, two of the beta-strands in the C-terminal domain have exchanged positions in order to maintain the location of essential active site residues in the context of the domain rotation. In ODC, the contacts in the dimer interface are formed primarily by the C-terminal domains, which interact through six aromatic rings that form stacking interactions across the domain boundary. The PLP binding site is formed by the C-termini of beta-strands and loops in the beta/alpha-barrel. In the native structure Lys69 forms a Schiff base with PLP. In both structures, the phosphate of PLP is bound between the seventh and eighth strands forming interactions with Arg277 and a Gly loop (residues 235-237). The pyridine nitrogen of PLP interacts with Glu274. DFMO forms a Schiff base with PLP and is covalently attached to Cys360. It is bound at the dimer interface and the delta-carbon amino group of DFMO is positioned between Asp361 of one subunit and Asp332 of the other. In comparison to the wild-type uncomplexed structure, Cys-360 has rotated 145 degrees toward the active site in the DFMO-bound structure. No domain, subunit rotations, or other significant structural changes are observed upon ligand binding. The structure offers insight into the enzyme mechanism by providing details of the enzyme/inhibitor binding site and allows for a detailed comparison between the enzymes from the host and parasite which will aid in selective inhibitor design.
...
PMID:X-ray structure of ornithine decarboxylase from Trypanosoma brucei: the native structure and the structure in complex with alpha-difluoromethylornithine. 1056

Ornithine decarboxylase (ODC) is a pyridoxal 5'-phosphate (PLP)-dependent enzyme that catalyzes the rate-determining step in the biosynthesis of polyamines. ODC is a proven drug target to treat African sleeping sickness. The x-ray crystal structure of Trypanosoma brucei ODC in complex with d-ornithine (d-Orn), a substrate analog, and G418 (Geneticin), a weak non-competitive inhibitor, was determined to 2.5-A resolution. d-Orn forms a Schiff base with PLP, and the side chain is in a similar position to that observed for putrescine and alpha-difluoromethylornithine in previous T. brucei ODC structures. The d-Orn carboxylate is positioned on the solvent-exposed side of the active site (si face of PLP), and Gly-199, Gly-362, and His-197 are the only residues within 4.2 A of this moiety. This structure confirms predictions that the carboxylate of d-Orn binds on the si face of PLP, and it supports a model in which the carboxyl group of the substrate l-Orn would be buried on the re face of the cofactor in a pocket that includes Phe-397, Tyr-389, Lys-69 (methylene carbons), and Asp-361. Electron density for G418 was observed at the boundary between the two domains within each ODC monomer. A ten-amino acid loop region (392-401) near the 2-fold axis of the dimer interface, which contributes several residues that form the active site, is disordered in this structure. The disordering of residues in the active site provides a potential mechanism for inhibition by G418 and suggests that allosteric inhibition from this site is feasible.
...
PMID:X-ray structure determination of Trypanosoma brucei ornithine decarboxylase bound to D-ornithine and to G418: insights into substrate binding and ODC conformational flexibility. 1267 97

The Epstein-Barr virus thwarts immune surveillance through a Gly-Ala repeat (GAr) within the viral Epstein-Barr virus-encoded nuclear antigen 1 protein. The GAr inhibits proteasome processing, an early step in antigen peptide presentation, but the mechanism of proteasome inhibition has been unclear. By embedding a GAr within ornithine decarboxylase, a natural proteasome substrate that does not require ubiquitin conjugation, we now demonstrate inhibition in a purified system, excluding involvement of ubiquitin conjugation or of proteins extraneous to substrate and proteasome. We show further that the GAr acts as a stop-transfer signal in proteasome substrate processing, resulting in vivo in partial proteolysis that halts just short of the GAr. Similarly, introducing a GAr into green fluorescent protein destabilized by the ornithine decarboxylase degradation domain also stops the progress of proteolysis, leading to the accumulation of partial degradation products. We postulate that the ATP motor of the proteasome slips when it encounters the GAr, impeding further insertion and, in this way, halting degradation.
...
PMID:Repeat sequence of Epstein-Barr virus-encoded nuclear antigen 1 protein interrupts proteasome substrate processing. 1468 54

Unlike other eukaryotes, which synthesize polyamines (PA) only from ornithine, plants possess an additional pathway utilizing arginine as a precursor. In this study, we have identified cDNA clones coding for a Glycine max ornithine decarboxylase (ODC, EC 4.1.1.7) and an arginine decarboxylase (ADC, EC 4.1.1.19). Expression analysis using semi-quantitative RT-PCR approach revealed that both genes coding for enzymes involved in putrescine biosynthesis (ODC and ADC) were found in most plant organs examined. Significant expression levels of both genes were detected in root tips and hypocotyls. The spatial distribution of GmODC and GmADC transcripts in primary and lateral roots and hypocotyls revealed that these genes are co-expressed in expanding cells of cortex parenchyma, expanding cells of central cylinder in main roots and in developing tissues and expanding cells of soybean hypocotyls. The data point out a correlation of the expression patterns of GmODC and GmADC gene to certain physiological roles such as organ development and cell expansion.
...
PMID:Ornithine decarboxylase and arginine decarboxylase gene transcripts are co-localized in developing tissues of Glycine max etiolated seedlings. 1576 62


1 2 Next >>

---