Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The growth of ZR-75-1 cells, a line of human breast cancer cells in culture, is stimulated by oestradiol and inhibited by anti-oestrogens. Changes in growth rate caused by these agents are accompanied by changes in activity of ornithine decarboxylase, a rate-limiting enzyme for polyamine synthesis. Furthermore, the growth inhibition caused by tamoxifen, an anti-oestrogen, can be reversed by the addition of spermine, spermidine or putrescine to the cells. Insulin can also stimulate ZR-75-1 cell growth and this is again accompanied by an increase in ODC activity. The reduced cell growth rate observed when the cells become confluent is associated with a marked decrease in ornithine decarboxylase activity. Experiments performed with DFMO, a specific and irreversible inhibitor of ODC, show that this compound can prevent the stimulation of growth by oestradiol and that this may be overcome by the addition of putrescine to the cells. It would appear that increased ODC activity and polyamine synthesis are necessary components of the stimulation of breast cancer cell growth by oestradiol but that other growth regulatory stimuli also may act via this enzyme.
Mol Cell Endocrinol 1986 Jun
PMID:Polyamines and growth regulation of cultured human breast cancer cells by 17 beta-oestradiol. 308 60

Trichomonas vaginalis, Tritrichomonas foetus and Trichomitus batrachorum grown in modified Diamond's medium all had high concentrations of putrescine and lower concentrations of spermidine and spermine. Ornithine decarboxylase (ODC; EC 4.1.1.17) was detectable in all three species although at significantly different levels. Trichomonas vaginalis had the highest activity (typically around 1.85 nmol min-1 (mg protein)-1), Trichomitus batrachorum the lowest (0.11 nmol min-1 (mg protein)-1). The Trichomonas vaginalis ODC had an apparent Mr of 230 000 and was severely inhibited by alpha-difluoromethylornithine (DFMO). S-Adenosyl-methionine decarboxylase (EC 4.1.1.50) could not be detected in T. batrachorum but was present in the other two species. Arginine decarboxylase was apparently absent from all three. All three trichomonad species were able to accumulate spermidine and putrescine from the medium. When T. vaginalis was grown in the presence of DFMO (4 mM), which had little effect on parasite growth, ODC activity was reduced by over 99% and the polyamine content was altered; putrescine concentrations were decreased, those of spermidine and spermine remained the same or were raised. DFMO-treated cells accumulated more exogenous putrescine than untreated control cells. The results suggest that the lack of effect of DFMO on T. vaginalis in culture was due to the parasite being able to accumulate polyamines from the growth medium. It appears, therefore, that testing DFMO and similar compounds in axenic trichomonad cultures may well not give a true indication of their effectiveness in vivo where sources of exogenous polyamines may not be available.
Mol Biochem Parasitol 1986 Jun
PMID:Polyamine biosynthesis in trichomonads. 309 Apr 33

When bloodstream forms of Trypanosoma brucei brucei were exposed to exogenous putrescine for 24 h during in vitro culture, the rate of O2 consumption increased significantly in a concentration-related and time-dependent manner. Trypanosomes cultured with 100 microM DL-alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase, were depleted of intracellular putrescine, and the rate of O2 consumption decreased by more than 50%. This effect could be abrogated if 100 microM putrescine was also present. A similar pattern was observed in trypanosomes harvested from rats after 36 h of DFMO treatment. If such trypanosomes were placed in culture for 2 h with 100 microM putrescine, the rate of O2 consumption returned to that of controls. When an intraperitoneal injection of putrescine was given to infected rats 18 h after commencement of DFMO treatment, rates of O2 consumption in the trypanosomes were found to return to control values. The addition of putrescine, spermidine or Mg2+ did not affect rate of O2 consumption in enriched mitochondrial preparations. However, when putrescine was present throughout the preparation of mitochondrial fractions, there was an increase of 23% in O2 uptake, which was 23% higher than in the controls. Putrescine may modulate trypanosomal respiration by stabilizing mitochondrial membranes.
Mol Biochem Parasitol 1986 Aug
PMID:Effect of putrescine on the respiration of Trypanosoma brucei brucei. 309 47

Procyclic Trypanosoma brucei brucei strain 366D is susceptible to DL-alpha-difluoromethylornithine (DFMO) with an in vitro ED50 value of 225 microM. A mutant of the procyclic strain resistant to 20 mM of DFMO was isolated by serial in vitro passages of the organisms in increasing concentrations of the drug. Drug resistance remains unchanged after at least ten serial passages in the absence of DFMO. The mutant contains the same level of ornithine decarboxylase activity as the wild-type procyclic, and the mutant enzyme exhibits a similar susceptibility toward DFMO as the wild type. Neither the rate of decarboxylation of ornithine, nor the membrane potential in the mutant cell is changed. The only observed change in the mutant is its significantly decreased uptake of DFMO which reaches a saturating level of 18 microM inside the cells; a concentration seven times below the Ki value of DFMO on T. brucei ornithine decarboxylase (130 microM). Apparently, the failure of DFMO uptake in the mutant strain has provided the basis of drug resistance. The results also raise the question on whether the uptake of DFMO by T. brucei is by passive diffusion or by transporter(s) mediation. DFMO does not compete with the uptake of ornithine, arginine or putrescine, and the reverse holds also true. However, the mutant strain cultivated under DFMO for several generations has a greatly enhanced uptake of ornithine and a moderately heightened uptake of putrescine. Both are reduced to the normal level upon further propagations of the mutant strain in the absence of DFMO.
Mol Biochem Parasitol 1987 Jan 02
PMID:A Trypanosoma brucei mutant resistant to alpha-difluoromethylornithine. 310 Sep 50

The biosynthesis of polyamines, a group of growth-related amines, varied in the rat pituitary gland with the different stages of the estrous cycle. The activity of ornithine decarboxylase (ODC), which catalyzes the rate-limiting step in the biosynthesis of polyamines, was greatly increased in the pituitary gland during the evening of proestrus. Ovariectomy resulted in a disappearance of this cyclic change in polyamine synthesis, whereas estrogen treatment of the ovariectomized rats gave rise to daily afternoon peaks in pituitary ODC activity. Like the prolactin cells, pituitary polyamine biosynthesis appeared to be regulated by dopamine. The induction of ODC activity in the pituitary gland during proestrus or after estrogen treatment was almost completely repressed by bromocriptine, a dopaminergic compound. The dopamine antagonist haloperidol, on the other hand, was a potent inducer of pituitary ODC activity. Neither pituitary DNA synthesis nor prolactin secretion, which both are induced by estrogen, were affected by inhibition of polyamine synthesis, suggesting a biological function of the pituitary polyamines unrelated to these events.
Mol Cell Endocrinol 1987 Jun
PMID:Dopaminergic regulation of polyamine synthesis in the rat pituitary gland. 310 79

Prolactin stimulated the citric acid content of the lateral lobe of the prostate of androgenized-hypophysectomized rats in a time-dependent manner. This stimulation of citric acid levels was not blocked by pretreatment of the animals with the ornithine decarboxylase (ODC) inhibitor, alpha-difluoromethyl ornithine (DFMO), suggesting that the prolactin induction of citric acid in this organ is not mediated through activation of the ODC. The efficacy of the dose of inhibitor used was monitored by analysis of the diamine product of ODC, putrescine. Further evidence of an independent control of citric acid and polyamine synthesis in the lateral lobe was provided by their differing age distributions in intact animals. ODC activity decreased sharply with age, whereas the tissue concentrations of citric acid remained relatively constant. Both studies suggest that although citric acid and ODC are modulated by prolactin, their synthesis or activation are controlled independently of each other.
Mol Cell Endocrinol 1987 Jul
PMID:Independent control of citrate production and ornithine decarboxylase by prolactin in the lateral lobe of the rat prostate. 311 26

The effect of D,L-alpha-difluoromethylornithine (DFMO) on thiol and polyamine levels in Trypanosoma brucei was investigated by isolating trypanosomes from infected rats treated with DFMO for 12-48 h. Concentrations of thiols, polyamines and other amino-compounds were measured by an automated high-performance liquid chromatography method. The levels of DFMO in rat plasma (0.02-1.34 mM) is similar to that found in the parasites (0.27-0.99 mM), concentrations which exceed the Ki of DFMO for T. brucei ornithine decarboxylase. Treatment with DFMO increases intracellular levels of ornithine, S-adenosylmethionine and decarboxylated S-adenosylmethionine and decreases putrescine and spermidine. Putrescine is undetectable after 12 h treatment with DFMO and after 48 h spermidine is decreased by 76%. By 48 h, the spermidine-glutathione conjugates glutathionylspermidine and dihydrotrypanothione (bis(glutathionyl)spermidine) are also decreased by 41 and 66%, respectively. In contrast, levels of glutathione show a slight increase. These changes in metabolite levels are consistent with the biosynthetic pathway proposed for Crithidia fasciculata, where trypanothione is synthesized from spermidine and glutathione via the intermediates N1- and N8-glutathionyl-spermidine. Trypanothione is thought to have two important roles in trypanosomatid metabolism: the maintenance of intracellular thiols in the correct redox state and in the removal of hydrogen peroxide and other hydroperoxides. Thus, it is proposed that depletion of this metabolite may be an important contributory factor to the selective toxic effect of DFMO, particularly in its synergistic effect with other trypanocidal drugs.
Mol Biochem Parasitol 1987 Jun
PMID:In vivo effects of difluoromethylornithine on trypanothione and polyamine levels in bloodstream forms of Trypanosoma brucei. 311 34

Procyclic Trypanosoma brucei grown in semi-defined media are sensitive to alpha-difluoromethylornithine (DFMO) (EC50 100 microM), an inhibitor of ornithine decarboxylase (ODC), a key enzyme in polyamine biosynthesis. Organisms resistant to 5 mM DFMO (EC50 greater than 20 mM) were obtained by passage in incremental amounts of drug. Resistant and wild-type cells accumulated DFMO by passive diffusion with a consequent decrease in polyamine levels, indicating inhibition of ODC in both cell types. The resistant phenotype was stable in the absence of DFMO, in which state there was no increase in ODC abundance or activity. By kinetic analysis, the ODC of resistant cells appeared normal. In wild-type and resistant cells, [3H]DFMO equally and uniquely affinity-labelled a 50 kDa polypeptide corresponding to the ODC subunit. Levels of ODC and tubulin mRNAs were elevated 4-fold in resistant cells grown in the presence of DFMO, although there was no indication of gene amplification. The intracellular concentration of dihydrotrypanothione (N1,N8-bis(glutathionyl)-spermidine), a redox intermediate unique to kinetoplastids, was unchanged in resistant cells growing in DFMO but was halved in wild-type cells exposed to DFMO for 48 h. The exceptionally elevated levels of ornithine found in DFMO-treated resistant cells most likely play a crucial role in cell survival by maintaining intracellular concentrations of dihydrotrypanothione by competing with DFMO for ODC.
Mol Biochem Parasitol 1987 Oct
PMID:Biochemical changes associated with alpha-difluoromethylornithine uptake and resistance in Trypanosoma brucei. 312 42

Activities of enzymes involved in transmethylation reactions were determined in bloodstream trypomastigotes of Trypanosoma brucei brucei infection in rats. S-Adenosyl-L-methionine synthetase (EC 2.5.1.6), S-adenosyl-L-homocysteine hydrolase (EC 3.3.1.1), cystathionine synthase (EC 4.2.1.21), as well as several transmethylases were detected and localized in cytosolic rather than particulate fractions. High performance liquid chromatography analysis of methionine cycle intermediates in cells from untreated rats and from rats treated with the ornithine decarboxylase inhibitor DL-alpha-difluoromethylornithine (DFMO) indicated that the inhibitor causes pronounced changes in concentrations of these intermediates and dramatically alters the methylation index of the cell. These findings demonstrate another in the wide range of metabolite disturbances attributable to DFMO and reflect the belief that multiple biochemical events are a sequel of its action on trypanosomes.
Mol Biochem Parasitol 1988 Jan 01
PMID:Effect of DL-alpha-difluoromethylornithine on methionine cycle intermediates in Trypanosoma brucei brucei. 312 29

Growth of Trichomonas vaginalis in a semi-defined medium was inhibited by 5 mM DL-alpha-difluoromethylornithine (DFMO). Using high pressure liquid chromatography (HPLC) analysis, putrescine and cadaverine levels were found to be 90 and 100% reduced, respectively after 120 h exposure, whilst spermidine and spermine levels were unchanged. Putrescine (40 microM) and cadaverine (6 microM) were detected in the spent media from control cultures. Neither of these diamines was detected in spent media from 72 h DFMO-treated cultures. Changes in intracellular levels of amine precursors were also determined by HPLC. There was a transient increase in ornithine to 39 nmol (mg protein)-1 at 48 h in the DFMO-treated cells while it remained undetectable in control cells throughout the experiment. Arginine and citrulline levels remained high, decreasing to control levels only after 72 h. Only spermine (1 mM) rescued DFMO-treated cells, and this is discussed with respect to the presence of a putative spermine-specific oxidase designated by its sensitivity to aminoguanidine. Aerobic incubation of growing (normal) cells with [14C]spermine resulted in the production of an unknown metabolite (19% of total label), whose content was reduced to 5% under anaerobic conditions. Decarboxylated S-adenosylmethionine remained undetectable in DFMO-treated cells, and the methylation index (ratio of S-adenosylmethionine to S-adenosylhomocysteine) did not change from the control value of 9.3. Ornithine decarboxylase, S-adenosylmethionine synthetase, S-adenosylmethionine:L-homocysteine methyltransferase, and S-adenosylhomocysteine hydrolase enzyme activities were detected. However, S-adenosylmethionine decarboxylase, spermidine synthase or spermine synthase were not detected. These findings are discussed with reference to the arginine dihydrolase pathway whose end products are putrescine and ATP.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Biochem Parasitol 1988 Oct
PMID:Effect of DL-alpha-difluoromethylornithine on polyamine synthesis and interconversion in Trichomonas vaginalis grown in a semi-defined medium. 314 9


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