Polyamines and their biosynthetic enzymes in Ehrlich ascites-carcinoma cells. Modification of tumour polyamine pattern by diamines.

1. Ehrlich ascites-carcinoma cells contained relatively high concentrations of spermidine and spermine, but the putrescine content of the washed cells was less than 10% of that of higher polyamines. 2. Ascites-tumour cells likewise exhibited high activities of L-ornithine decarboxylase (EC 4.1.1.17), S-adenosyl-L-methionine decarboxylase (EC 4.1.1.50), spermidine synthase (EC 2.5.1.16) and spermine synthase. 3. During the first days after the inoculation, the polyamine pattern of the ascites cells was characterized by a high molar ratio of spermidine to spermine, which markedly decreased on aging of the cells. 4. Various diamines injected into mice bearing ascites cells rapidly and powerfully decreased ornithine decarboxylase activity in the carcinoma cells, apparently through a mechanism that was not a direct inhibition of the enzyme in vitro. Cadaverine (1,5-diaminopentane) and 1,6-diaminohexane were the most potent inhibitors of ornithine decarboxylase among the amines tested. 5. Chronic treatment of the mice with diamines resulted in a virtually complete disappearance of ornithine decarboxylase activity, and after 24h a significant decline in spermidine accumulation. 6. Cadaverine appeared to be an especially suitable compound for use as an inhibitor of the synthesis of higher polyamines, at least in Ehrlich ascites cells, since this diamine also acted as a competitive inhibitor for putrescine in the spermidine synthase reaction without being incorporated into the higher polyamines.     

Studies on polyamine biosynthesis in Euglena gracilis.

Euglene gracilis (strain Z) was found to contain five polyamines which could be separated by high-pressure cation-exchange chromatography. 1,3-Diaminopropane, putrescine, norspermidine (N-(3-aminopropyl)-1,3-diaminopropane), spermidine and norspermine (N,N'-bis(aminopropyl)-1,3-diaminopropane) were identified. Biosynthesis of putrescine in E. gracilis proceeds through decarboxylation of L-ornithine, no arginine decarboxylase (EC 4.1.1.19) activity could be detected. The properties of the enzymes ornithine decarboxylase (EC 4.1.1.17) and S-adenosylmethionine decarboxylase (EC 4.1.1.50) in this alga were found to be similar to those of the enzymes isolated from animal tissues or yeast cells. A bioxynthetic scheme is proposed which relates the different polyamines occurring in E. gracilis.     

Inhibition of ornithine decarboxylase activity and spermidine accumulation in regenerating rat liver.

Injections of 1,3-diaminopropane, a close structural analogue of putrescine (1,4-diaminobutane), into partially hepatectomized rats powerfully inhibited ornithine decarboxylase (EC 4.1.1.17) activity in the regenerating liver in vivo. The compound did not have any effect on the enzyme activity in vitro (under assay conditions employed) but appeared to exert an inhibitory influence on the synthesis of ornithine decarboxylase itself.Repeated injections of diaminopropane into rats after partial hepatectomy, starting at the time of the operation and continued until 33 h postoperatively, markedly diminished the stimulation of ornithine decarboxylase activity in the regenerating liver remnant, and completely prevented the increases in hepatic spermidine concentration normally occurring in response to partial hepatectomy.Treatment of the rats with diaminopropane did not depress the activity of adenosylmethionine decarboxylase (EC 4.1.1.50) in the regenerating liver. Nor did the compound have any effect, whatsoever, on the activity of spermidine synthase (EC 2.5.1.16) in vitro, thus obiviously proving that the increased accumulation of liver spermidine after partial hepatectomy primarily depends upon a stimulation of ornithine decarboxylase activity and a concomitant accumulation of putrescine. The results also showed that 1,3-diamino-propane could not replace putrescine in the synthesis of higher polyamines in rat liver. The inhibition of ornithine decarboxylase by diaminopropane thus appears to represent “gratuitous” repression of polyamine biosynthesis and might conceivably be used for studies devoted to the elucidation of the physiological functions of natural polyamines.     

Control of utilization of L-arginine, L-ornithine, agmatine, and putrescine as nitrogen sources in Escherichia coli K-12.

The regulation of the synthesis of the enzymes involved in the utilization of L-arginine, L-ornithine, agmatine, and putrescine as a sole nitrogen source in Escherichia coli K-12 was examined. The synthesis of agmatine ureohydrolase, putrescine aminotransferase, and pyrroline dehydrogenase is dually controlled by catabolite repression and nitrogen availability. Catabolite repression of agmatine ureohydrolase, but not that of putrescine aminotransferase or pyrroline dehydrogenase, is relieved by the addition of cAMP. Agmatine ureohydrolase synthesis in addition is subject to induction by L-arginine and agmatine. Arginine decarboxylase and ornithine decarboxylase synthesis is not sensitive to catabolite repression or to stimulation by nitrogen limitation or subject to substrate induction.     

Regulation of polyamine synthesis in physarum polycephalum during growth and differentiation

The levels and synthesis of polyamines were investigated in Physarum polycephalum to obtain information about their regulation during growth and differentiation in a lower eukaryote. Putrescine pools rapidly increased 4–5 fold during the change from dormant spherules to growing plasmodia. The activity of ornithine decarboxylase (EC 4.1.1.17), which converts ornithine to putrescine, reflected this rapid change in the level of putrescine. Spermidine levels were closely correlated with protein concentrations during differentiation due to variations in the activity of S-adenosyl-l-methionine decarboxylase which is involved in the conversion of putrescine to spermidine This enzyme was not stimulated by putrescine, unlike the similar enzyme in other eukaryotes, thereby permitting independent regulation of putrescine and spermidine levels. The high levels of both putrescine and spermidine suggest separate functions for these polyamines in Physarum.The half-lives of ornithine decarboxylase and S-adenosyl-l-methionine decarboxylase were 14 and 21.5 min, respectively. These short half-lives keep the polyamine metabolism under a very tight control as illustrated by the rapid fluctuations in enzyme activity during differentiation and the synchronous mitotic cycle. The step patterns of these unstable enzymes during the mitotic cycle suggest that these enzyme levels are limited by gene dosage.     

Specific inhibition of the synthesis of putrescine and spermidine by 1,3-diaminopropane in rat liver in vivo.

Chronic administration of 1,3-diaminopropane, a compound inhibiting mammalian ornithine decarboxylase (EC 4.1.1.17) in vivo, effectively prevented the large increases in the concentration of putrescine that normally occur during rat liver regeneration. Furthermore, repeated injections of diaminopropane depressed by more than 85% ornithine decarboxylase activity in rat kidney. Administration of diaminopropane 60 min before partial hepatectomy only marginally inhibited ornithine decarboxylase activity at 4 h after the operation. However, when the compound was given at the time of the operation (4 h before death), or any time thereafter, it virtually abolished the enhancement in ornithine decarboxylase activity in regenerating rat liver remnant. An injection of diaminopropane given 30 to 60 min after operation, but not earlier or later, depressed S-adenosyl-L-methionine decarboxylase activity (EC 4.1.1.50) 4 h after partial hepatectomy. Diaminopropane likewise inhibited ornithine decarboxylase activity during later periods of liver regeneration. In contrast to early regeneration, a total inhibition of the enzyme activity was only achieved when the injection was given not earlier than 2 to 3 h before the death of the animals. Diaminopropane also exerted an acute inhibitory effect on adenosylmethionine decarboxylase activity in 28-h regenerating liver whereas it invariably enhanced the activity of tyrosine aminotransferase (EC 2.6.1.5), used as a standard enzyme of short half-life. Treatment of the rats with diaminopropane entirely abolished the stimulation of spermidien synthesis in vivo from [14C]methionine 4 h after partial hepatectomy or after administration of porcine growth hormone. Both partial hepatectomy and the treatment with growth hormone produced a clear stimulation of hepatic RNA synthesis, the extent of which was not altered by injections of diaminopropane in doses sufficient to prevent any enhancement of ornithine decarboxylase activity and spermidine synthesis.     

The biochemistry, genetics, and regulation of polyamine biosynthesis in Saccharomyces cerevisiae

We have studied the enzymes and genes involved in the biosynthesis of putrescine, spermidine, and spermine in Saccharomyces cerevisiae. Mutants have been isolated with defects in the biosynthetic pathway as follows: spe10 mutants, deficient in ornithine decarboxylase, cannot make putrescine, spermidine, or spermine; spe2 mutants, lacking S-adenosylmethionine decarboxylase, cannot make spermidine or spermine; spe3 mutants, lacking putrescine aminopropyltransferase, cannot make spermidine or spermine; and spe4 and spe40 mutants, lacking spermidine aminopropyltransferase, contain no spermine and permit growth of spe10 mutants. Studies with these mutants have shown that in yeast: 1) polyamines are absolutely required for growth; 2) putrescine is formed only by decarboxylation or ornithine; 3) two separate aminopropyltransferases are required for spermidine and spermine synthesis; 4) spermine and spermidine are important in the regulation of ornithine decarboxylase and the amines exert this control by a posttranslational modification of the enzyme; and 5) spermidine or spermine is essential for sporulation of yeast and for the maintenance of the double-stranded RNA killer plasmid. Recent studies in amine-deficient mutants of Escherichia coli have shown an important role of the polyamines in protein synthesis in vivo.     

Non-competitive inhibition of ornithine decarboxylase by a phosphopeptide and phosphoamino acids

In Tetrahymena pyriformis the cytosolic ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17) activity is considerably inhibited by the presence of polyamines in the growth medium, while the nuclear ornithine decarboxylase is only slightly affected. Experimental evidence suggests that the presence of putrescine and/or spermidine elicits the appearance of non-competitive inhibitors of ornithine decarboxylase. One of the inhibitors has a molecular weight of 25,000 and properties of antizyme. In addition, two other low molecular weight inhibitors are extracted, one which is a phosphoserine oligopeptide, and the other which is phosphotyrosine. All inhibit non-competitively the homologous and heterologous (Escherichia coli and rat liver) ornithine decarboxylases. Similarly, non-competitive inhibition was obtained when the commercially available phosphoamino acids were tested against the already mentioned ornithine decarboxylases.     

Early events in the response of fast skeletal muscle to chronic low-frequency stimulation. Polyamine biosynthesis and protein phosphorylation.

The concentrations of putrescine, spermidine and spermine and the activities of ornithine decarboxylase (ODC) and S-adenosyl-L-methionine decarboxylase (SAM-D) were investigated in fast muscle subjected to chronic low-frequency electrical stimulation. Both ODC and SAM-D activities increased markedly between 18 and 48 h of stimulation. Changes in enzyme activities were followed by phasic elevations in the concentrations of putrescine, spermidine and spermine. Peak levels were reached first by putrescine at 3-4 days, followed by spermidine at about 9 days and then by spermine at about 11 days. A possible relationship was sought between these events and changes produced in vitro in the phosphorylation pattern of cytoplasmic proteins and the total activity of cyclic AMP-dependent protein kinase. However, during the early stages of stimulation, no prominent changes were seen either in the phosphorylation pattern or in the activity of cyclic AMP-dependent protein kinase. These characteristics changed significantly at a later stage (by 12 days of stimulation) and became indistinguishable from those of slow muscle by 3 to 4 weeks of stimulation.     

Metabolism of polyamines by cultured glioma cells. Effect of asparagine on gamma-aminobutyric acid concentrations.

The activity of ornithine decarboxylase (EC 4.1.1.17) increased in confluent cultures of glioma C6BU-1 cells 3 h after adding a complete serum-containing medium, and was maximal 5 h later. The activity of S-adenoxyl-L-methionine decarboxylase (EC 4.1.1.50) increased soon after addition of the complete medium to the cells, and reached its peak after 11 h. The activity of diamine oxidase (EC 1.4.3.6) also increased soon after adding complete medium and was maximal 8h later, when the activity of ornithine decarboxylase reached its peak. The increase in the activity of S-adenosyl-L-methionine decarboxylase was accompanied by changes in cellular spermidine and spermine concentrations, whereas the increase in the activity of diamine oxidase was followed by the accumulation of gamma-aminobutyric acid, which was detected both in the cells and in the medium. Asparagine enhanced the utilization of radioactive putrescine by glioma cells suspended in buffered-salt/glucose solution and increased intracellular and extracellular gamma-aminobutyric acid concentrations. Radioactive putrescine was converted into spermidine and spermine by glioma cells after addition of a serum-containing medium, but not after adding buffered--salt/glucose solutions, in the presence or absence of asparagine. The kinetics of ornithine decarboxylase 'induction' and the half-life of the enzyme differed in cells incubated with buffered asparagine solutions and serum-containing media.     

Regulation of putrescine metabolism in Ehrlich ascites carcinoma cells exposed to hypotonic medium

When exposed to hypotonic growth medium, Ehrlich ascites carcinoma cells showed a rapid stimulation of ornithine decarboxylase (EC 4.1.1.17) activity in 4 h, followed by a rise in their putrescine content. This effect was totally abolished by addition of a slightly hypertonic concentration of sodium chloride or sucrose to the medium. The general protein synthesis was unaffected by the hypotonic treatment. The uptake of putrescine and, to a lesser extent, spermidine was enhanced, and the conversion of the radioactive putrescine into spermidine appeared partially inhibited during later stages of the hypotonic treatment. As a result, the half-life of putrescine increased from 2.8 h under isoosmotic conditions to 7.3 h in hypoosmotic medium. Both exogenous ([¹⁴C]-putrescine-derived) and endogenous ([¹⁴C]ornithine-derived) putrescine degraded at similar rates in control and hypotonic cells, yet the putrescine taken from the medium degraded preferably to nonpolyamine products, while the putrescine synthesized in the cell was converted evenly to spermidine and to other metabolites. Adenosylmethionine decarboxylase activity (EC 4.1.1.50), which provides the second precursor for spermidine and spermine synthesis, was distinctly inhibited in the hypotonic medium. Inhibition was likewise observed in spermidine synthase activity, while spermine synthase was marginally stimulated. It appears that the hypotonic treatment serves a special condition under which not only the formation of putrescine is enhanced dramatically but the cells also attempt to conserve the diamine by preventing its further metabolism to higher polyamines.     

Decarboxylases for polyamine biosynthesis in Drosophila melanogaster larvae.

Ornithine decarboxylase (L-ornithine carboxy-lase, EC 4.1.1.17) and S-adenosyl-methionine decarboxylase (S-adenosyl-L-methionine carboxy-lase, EC 4.1.1.50) were assayed in Drosophilia melanogaster larvae. The highest enzyme activities were detected in 24 and 48 h larvae, with diminishing activities in subsequent larval stages. Stimulation of S-adenosylmethionine decarboxylase by putrescine was demonstrable in late but not in early stages of larval development.     

Regulatory mutations affecting ornithine decarboxylase activity in Saccharomyces cerevisiae.

We isolated several strains of Saccharomyces cerevisiae containing mutations mapping at a single chromosomal gene (spe10); these strains are defective in the decarboxylation of L-ornithine to form putrescine and consequently do not synthesize spermidine and spermine. The growth of one of these mutants was completely eliminated in a polyamine-deficient medium; the growth rate was restored to normal if putrescine, spermidine, or spermine was added. spe10 is not linked to spe2 (adenosylmethionine decarboxylase) or spe3 (putrescine aminopropyltransferase [spermidine synthease]). spe 10 is probably a regulatory gene rather than the structural gene for ornithine decarboxylase, since we isolated two different mutations which bypassed spe10 mutants; these were spe4, an unliked recessive mutation, and spe40, a dominant mutation linked to spe10. Both spe4 and spe40 mutants exhibited a deficiency of spermidine aminopropyltransferase (spermine synthase), but not of putrescine aminopropyltransferase. This suggests that ornithine decarboxylase activity is negatively controlled by the presence of spermidine aminopropyltransferase.     

Effects of epidermal growth factor on the syntheses of DNA and polyamine in isoproterenol-stimulated murine parotid gland

The effects of epidermal growth factor (EGF) on isoproterenol (IPR)-stimulated DNA synthesis and the activities of the rate limiting enzymes of polyamine synthesis (ornithine and S-adenosylmethionine decarboxylases) in parotid glands were investigated in vitro in cultured rat parotid explants and in vivo in submandibulectomized mice (mice after bilateral removal of the submandibular and sublingual glands). When the explants were cultured on siliconized lens paper floating on chemically defined synthetic medium, IPR caused the increases of both tissue cAMP level and the two decarboxylase activities in the prereplicative period and the stimulation of DNA synthesis with similar time courses to those observed in vivo. Dibutyryl cyclic AMP (DBcAMP) also increased the enzyme activities, but not DNA synthesis. EGF (1-2 ng/ml) had little effect on the IPR- and DBcAMP-dependent increases of amylase secretion and the enzyme activities, but it markedly enhanced IPR-stimulated DNA synthesis. Moreover, increase in DNA synthesis by DBcAMP was clearly observed in the presence of EGF when the explants were treated with this nucleotide analogue only during the early prereplicative period. In in vivo experiments, IPR-dependent increase in DNA synthesis was less in submandibulectomized mice than in intact animals. This decreased response to IPR of DNA synthesis was completely reversed by administration of EGF, though EGF alone did not induce either the enzymes or DNA synthesis. In submandibulectomized mice, although increases in the enzyme activities 8 h after injection of IPR were lower and they were significantly reversed by EGF, the activities at 12 h and the changes in polyamine levels at 8 and 12 h were almost the same as those in intact mice and were not affected by EGF treatment. These results obtained in vitro and in vivo suggest that EGF participates in the maximal response of IPR-dependent DNA synthesis but is not involved in the change of polyamine synthesis induced by IPR in murine parotid glands.     

Effect of inhibitors of protein synthesis on rat liver spermidine N-acetyltransferase

The increase in spermidine N-acetyltransferase activity in rat liver produced by carbon tetrachloride was completely prevented by simultaneous treatment with inhibitors of protein and nucleic acid synthesis suggesting that the increase results from the synthesis of new protein rather than the release of the enzyme from a cryptic inactive form. Treatment with cycloheximide 2 h after carbon tetrachloride also completely blocked the rise in spermidine N-acetyltransferase seen 4 h later. Such treatment completely prevented the fall in spermidine and rise in putrescine in the liver 6 h after carbon tetrachloride confirming the importance of the induction of spermidine N-acetyltransferase in the conversion of spermidine into putrescine. When cycloheximide was administered to rats in which spermidine N-acetyltransferase activity had been stimulated by prior treatment with carbon tetrachloride or thioacetamide, the activity was lost rapidly showing that the enzyme protein has a rapid rate of turnover. The half-life for the enzyme in thioacetamide-treated rats was 40 min, whereas the half-life for ornithine decarboxylase (which is well known to turn over very rapidly) was 27 min. In carbon tetrachloride-treated rats the rate or protein degradation was reduced and the half-life of spermidine N-acetyltransferase was 155 min and that for ornithine decarboxylase was 65 min. It appears that three of the enzymes involved in the synthesis and interconversion of putrescine and spermidine namely, ornithine decarboxylase, S-adenosylmethionine decarboxylase and spermidine N-acetyltransferase have rapid rates of turnover and that polyamine levels are regulated by changes in the amount of these enzymes.     

Polyamine metabolism in Acanthamoeba: polyamine content and synthesis of ornithine, putrescine, and diaminopropane

Five polyamines which could be separated by high performance liquid chromatography were found in Acanthamoeba castellanii (strain Neff). These included in order of decreasing abundance: 1,3-diaminopropane, spermidine, spermine, norspermidine, and putrescine. Only diaminopropane and norspermidine had been found previously. Spermine was present in cultures grown in broth, but not in defined medium. Radioactive substrates were used to establish that putrescine was synthesized by decarboxylation of ornithine, ornithine was synthesized from arginine or citrulline, and diaminopropane was synthesized from spermidine. The presence of ornithine decarboxylase (EC 4.1.1.17), arginase (EC 3.5.3.1), and urease (EC 3.5.1.5) and the absence of arginine decarboxylase (EC 4.1.1.19) were established. A scheme for polyamine biosynthesis in A. castellanii is proposed.     

Uptake of polyamines by the unicellular green alga Chlamydomonas reinhardtii and their effect on ornithine decarboxylase activity

Uptake of exogenous polyamines by the unicellular green alga Chlamydomonas reinhardtii and their effects on polyamine metabolism were investigated. Our data show that, in contrast to mammalian cells, Chlamydomonas reinhardtii does not contain short-living, high-affinity polyamine transporters whose cellular level is dependent on the polyamine concentration. However, exogenous polyamines affect polyamine metabolism in Chlamydomonas cells. Exogenous putrescine caused a slow increase of both putrescine and spermidine and, vice versa, exogenous spermidine also led to an increase of the intracellular levels of both spermidine and putrescine. No intracellular spermine was detected under any conditions. Exogenous spermine was taken up by the cells and caused a decrease in their putrescine and spermidine levels. As in other organisms, exogenous polyamines led to a decrease in the activity of ornithine decarboxylase, a key enzyme of polyamine synthesis. In contrast to mammalian cells, this polyamine-induced decrease in ornithine decarboxylase activity is not mediated by a polyamine-dependent degradation or inactivation, but exclusively due to a decreased synthesis of ornithine decarboxylase. Translation of ornithine decarboxylase mRNA, but not overall protein biosynthesis is slowed by increased polyamine levels.     

Polyamine Metabolism in Acanthamoeba: Polyamine Content and Synthesis of Ornithine,Putrescine, and Diaminopropane1

Five polyamines which could be separated by high performance liquid chromatography were found in Acanthamoeba castellanii (strain Neff). These included in order of decreasing abundance: 1,3-diaminopropane, spermidine, spermine, norspermidine, and putrescine. Only diaminopropane and norspermidine had been found previously. Spermine was present in cultures grown in broth, but not in defined medium. Radioactive substrates were used to establish that putrescine was synthesized by decarboxylation of ornithine, ornithine was synthesized from arginine or citrulline, and diaminopropane was synthesized from spermidine. The presence of ornithine decarboxylase (EC 4.1.1.17), arginase (EC 3.5.3.1), and urease (EC 3.5.1.5) and the absence of arginine decarboxylase (EC 4.1.1.19) were established. A scheme for polyamine biosynthesis in A. castellanii is proposed.     

Polyamine biosynthesis and DNA synthesis in cultured mammary gland explants from virgin mice

The mammary cells in virgin mice are essentially non-proliferative, but they can be induced to undergo DNA synthesis in vitro in the presence of insulin. Time course studies on polyamine biosynthesis and DNA synthesis showed that insulin elicits sequential stimulation of the activity of the polyamine biosynthetic enzymes, ornithine decarboxylase, S-adenosyl-L-methionine decarboxylase (SAMDC) and spermidine synthase, and an increase in the concentration of spermidine prior to the augmentation of DNA synthesis. At 48 to 72 hours of culture when DNA synthesis is maximal, the concentration of spermidine increased 2? to 3-fold, whereas the level of spermine remained unchanged. Addition of methyl glyoxal bis(guanylhydrazone) (5—10 μM), a potent inhibitor of SAMDC, to the medium at the onset of culture resulted in inhibition of spermidine formation and DNA synthesis, but when added at 24 hours or 48 hours of culture, the inhibitory effect on DNA synthesis was greatly reduced. The drug, however, produced little inhibition of RNA and protein synthesis. Inhibition of DNA synthesis by the drug can be reversed by addition of spermidine or other polyamines such as putrescine, cadaverine and spermine to the culture. Spermidine is, however, the only polyamine that is effective at physiological concentrations (100～150 pmoles/mg tissue). These results suggest a possibility that spermidine may play a key role in the regulation of mammary cell proliferation.     

Cellular content and biosynthesis of polyamines during rooster spermatogenesis.

The natural polyamines spermine and spermidine, and the diamine putrescine, were extracted from rooster testis cells separated by sedimentation at unit gravity, and from vas-deferens spermatozoa. The ratios spermine/DNA and spermidine/DNA were kept relatively constant throughout spermatogenesis, whereas the ratio putrescine/DNA rose in elongated spermatids. The cellular content of spermine, spermidine and putrescine decreased markedly in mature spermatozoa. Two rate-limiting enzymes in the biosynthetic pathway of polyamines, ornithine decarboxylase and S-adenosyl-L-methionine decarboxylase, showed their highest activities at the end of spermiogenesis and were not detectable in vas-deferens spermatozoa. A marked reduction in cell volume during spermiogenesis without a parallel decrease in the cellular content of polyamines suggests the possibility that the marked changes in chromatin composition and structure occurring in rooster late spermatids could take place in an ambience of high polyamine concentration.