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T O Eloranta

Publications and source records attributed to T O Eloranta.

34 records · Page 2Linked to original sources
PubMed1989

Synthesis and analysis of selenomethionine metabolites.

This paper describes the enzymatic synthesis of selenomethionine metabolites of the transmethylation and polyamine synthesis pathways: adenosylselenomethionine, adenosylselenohomocysteine, decarboxylated adenosylselenomethionine, and methylselenoadenosine. These compounds and the corresponding methionine metabolites were simultaneously separated by a single HPLC run. The sensitivity of the HPLC method is about 20 pmol per compound. The method may be used for direct analysis of the metabolite levels in tissues or cells treated with selenomethionine and it provides an assay method for the pulse-chase type of analysis of relative flows for both selenium- and sulfur-containing compounds in transmethylation and polyamine pathways.

Chromatography, High Pressure Liquid↗
PubMed1989

Effects of dietary polyamine precursors on the metabolism and tissue concentrations of amino acids in the rat.

Experiments were conducted to determine the effects of dietary supplements of amino acid precursors of polyamines on amino acid metabolism in the rat in order to better understand comparative aspects of polyamine metabolism. Rats were fed isonitrogenous combinations of methionine, ornithine, arginine and 2-difluoromethylornithine in casein-based diets. It was observed that hepatic concentrations of methionine, 5'-deoxy-5'-methylthioadenosine and decarboxylated S-adenosylmethionine were more easily influenced by diet than were arginine and metabolites. It was concluded that rats may be more refractory to exogenous polyamine precursor amino acids than are chicks because of the presence of a functional urea cycle.

Adenosine↗
PubMed1989

Effect of human mast cell tryptase on human plasma proenzymes.

The effect of human skin mast cell tryptase on human plasma proenzymes (prothrombin, coagulation factor XII, complement C1s, protein C and plasminogen) was investigated. Tryptase had no effect on these proenzymes, when incubated with them at 37 degrees C for up to 90 min, as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by the ability to hydrolyze specific peptide p-nitroanilide substrates. After prolonged treatment with tryptase, proenzymes could be fully activated with their specific activators. The results indicate that tryptase neither activates these plasma proenzymes nor inactivates the corresponding active enzymes. As a positive control, the tryptase preparation was also incubated with human fibrinogen and rat thymus histones. Prolonged treatment with tryptase increased the thrombin-induced clotting time of fibrinogen. Tryptase also efficiently hydrolyzed histone H1 from rat thymus. Histones H3/H2B and H2A were hydrolyzed less efficiently than H1, and no hydrolysis of histone H4 by tryptase was detected under the experimental conditions.

Animals↗
PubMed1988

The allosteric effect of salt on human mast cell tryptase.

The inhibitory effect of potassium chloride and ammonium sulphate on purified human skin tryptase and bovine trypsin was studied enzyme-kinetically, using Z-Gly-Pro-Arg-pNA, Z-Gly-Pro-Arg-AMC, benzoyl-L-arginine ethyl ester (BAEE) and tosyl-L-arginine methyl ester (TAME) as substrates. With increasing salt concentrations, the curve of reaction velocity vs. substrate concentration changed from hyperbolic to sigmoidal when anilide substrates (Z-Gly-Pro-Arg-pNA or -AMC) were used. Only the Km value increased, while the Vmax value remained unchanged. The trend was similar with BAEE or TAME as the substrates. However, the effect of salt on the hydrolysis of these ester substrates was not as strong as on the hydrolysis of anilide substrates, and sigmoidal kinetics were not observed even at the highest KCl concentration (0.7 M) used. Heparin, used as a stabilizer, had no influence on this phenomenon, but it did slightly decrease the apparent Km and Vmax values in low-salt conditions. By comparison, trypsin was not as strongly affected by salt as tryptase, and the inhibition type was mixed competitive and non-competitive. The present results indicate that the salt acts on tryptase as an allosteric effector, and this should be carefully considered when enzyme kinetic parameters and enzyme activity of skin tryptase are measured.

Ammonium Sulfate↗
PubMed1988

1-Aminooxy-3-aminopropane reversibly prevents the proliferation of cultured baby hamster kidney cells by interfering with polyamine synthesis.

The effects on cultured baby hamster kidney cells of 1-aminooxy-3-aminopropane, a potent new inhibitor of mammalian ornithine and S-adenosylmethionine decarboxylases and of spermidine synthase, were studied. At 0.5 mM concentration in the culture medium, the drug did not interfere with the transmethylation-transsulfuration pathway nor with the polyamine transport system, but it blocked the proliferation and macromolecule synthesis of the cells and reduced the cellular spermidine level to less than 10% of the control value at identical cell density. These changes were accompanied by a total cessation of the excretion of putrescine, spermidine, and acetylated polyamines into the culture medium, greatly increased activity of ornithine and S-adenosylmethionine decarboxylases, and an accumulation of both decarboxylated and intact S-adenosylmethionine. These effects were reversed by the removal of the inhibitor from the culture medium or by supplementing the medium with either 0.5 mM putrescine or 0.1 mM spermidine. In the former case, however, a lag period of 24 h was necessary for the cells to recover. The elevated concentration of decarboxylated S-adenosylmethionine normalized very slowly but apparently had no harmful effects on the cells. The clonigenic potential of the cells was only slightly reduced by prolonged treatment with 0.5 mM 1-aminooxy-3-aminopropane. Thus, the new drug is not toxic to the cells, but either directly or indirectly stops their proliferation by preventing the adequate formation of putrescine and spermidine.

Acetyltransferases↗
PubMed1987

Effect of dietary methionine, arginine and ornithine on the metabolism and accumulation of polyamines, S-adenosylmethionine and macromolecules in rat liver and skeletal muscle.

The interrelationship and possible causality of polyamine synthesis and the transmethylation pathway in the growth-retarding effects of inadequate or excess dietary methionine was studied in young male rats. Feeding the rats for 2 weeks diets containing toxic concentrations of methionine had no effect on polyamine and S-adenosylmethionine metabolism in skeletal muscle, but resulted in markedly elevated concentrations of S-adenosylmethionine and S-adenosylhomocysteine and slightly decreased accumulation of spermine and RNA in the liver. These changes were accompanied by liver-specific stimulation of methionine adenosyltransferase and reduction of spermine synthase activities. Inadequate arginine feeding or supplementation of the diets with ornithine or excess arginine resulted in no apparent changes in tissue methionine or polyamine metabolism and did not alleviate the effects of varied dietary methionine supply. Inhibition of putrescine synthesis by supplementing the diets with 2-difluoromethylornithine did not modify the effects of toxic concentrations of dietary methionine. It is suggested that although hepatic spermine synthase is sensitive to excess methionine feeding, methionine toxicity is not mediated by defective polyamine metabolism.

Amino Acids↗
PubMed1984

Catabolism and lability of S-adenosyl-L-methionine in rat liver extracts.

The fate of S-adenosyl-L-methionine was studied in rat liver extracts by analysing the distribution of radioactivity from labelled adenosylmethionine in decomposition products, which were separated from each other by chromatographic and electrophoretic means. Marked non-enzymic degradation to adenine, pentosylmethionine, methylthioadenosine and homoserine was evident at pH 6.9-7.8. Enzymic cleavage to methylthioadenosine was stoichiometric with the accumulation of spermidine and could be totally prevented by inhibiting S-adenosyl-L-methionine decarboxylase. The results rule out the existence of adenosylmethionine cyclotransferase in rat liver and indicate that only two quantitatively significant enzymic processes are involved in hepatic adenosylmethionine degradation. Excluding nonenzymic decomposition, more than 99% of adenosylmethionine is demethylated and exclusively catabolized further by S-adenosyl-L-homocysteine hydrolase. Less than 1% of adenosylmethionine is decarboxylated and immediately utilized totally for polyamine biosynthesis.

Adenosine↗
PubMed1982

Uptake and utilization of 5'-methylthioadenosine by cultured baby-hamster kidney cells.

5'-Methylthioadenosine was taken up and immediately metabolized further by cultured baby-hamster kidney cells during the exponential phase of growth. The adenine moiety supplied the purine-nucleotide pool via the salvage pathway and was efficiently incorporated into nucleic acids. Catabolites of methylthioadenosine excreted by the cells included adenine, purinic compounds and metabolites of the ribose portion. 5'-Methylthiotubercidin had no significant effect on the cellular metabolism of methyl-thioadenosine, but greatly inhibited its uptake. erythro-9-(2-Hydroxy-3-nonyl)adenine had no effect on the uptake, but markedly interfered with the further utilization of methylthioadenosine after cleavage in the cells.

Adenine↗
PubMed1982

Effect of 9-beta-D-arabinofuranosyladenine and erythro-9-(2-hydroxy-3-nonyl) adenine on the metabolism of S-adenosylhomocysteine, S-adenosylmethionine, and adenosine in rat liver.

The effects of arabinosyladenine, an antiviral and antitumor agent used therapeutically, on the metabolism of adenosylhomocysteine were studied in rat liver. A rapid but transient accumulation of adenosylhomocysteine and adenosylmethionine was observed after a single i.p. injection of the adenosine analogue. The extent and duration of the accumulation was increased by multiple doses of arabinosyladenine and by giving the nucleoside in combination with erythro-9-(2-hydroxy-3-nonyl)-adenine, a potent inhibitor of adenosine deaminase, which significantly increased its concentration in the liver. Hepatic adenosine concentration was also enhanced by the treatment but less dramatically. Accumulation of adenosylhomocysteine resulted from a rapid but reversible in vivo inactivation of adenosylhomocysteine hydrolase. Approximately 10% of the hydrolase activity persisted despite the inactivation treatment. After four injections with arabinosyladenine (200 mumol/kg body wt.) in combination with the adenosine deaminase inhibitor (50 mumol/kg body wt.), given at 1 h intervals, the concentration of adenosylhomocysteine was increased 30-fold and that of adenosylmethionine 5-fold as compared with the control values. The concentrations remained at that level for at least 2 h and then gradually declined to the control level. The activity of adenosylhomocysteine hydrolase stayed at the 10% level for several hours but returned to the control level within 24 h of the last injection. The results show that prolonged treatment with arabinosyladenine, especially in combination with an adenosine deaminase inhibitor, causes marked but reversible changes in methionine metabolism, resulting in the hepatic accumulation of adenosylhomocysteine to a level that is likely to interfere with biological methylation reactions. This offers an additional mechanism by which arabinosyladenine may evoke toxic effects in animal cells.

Adenine↗
PubMed1977

S-adenosylmethionine metabolism and its relation to polyamine synthesis in rat liver. Effect of nutritional state, adrenal function, some drugs and partial hepatectomy.

S-Adenosylmethionine metabolism and its relation to the synthesis and accumulation of polyamines was studied in rat liver under various nutritional conditions, in adrenalectomized or partially hepatectomized animals and after treatment with cortisol, thioacetamide or methylglyoxal bis(guanylhydrazone) {1,1'-[(methylethanediylidine)dinitrilo]diguanidine}. Starvation for 2 days only slightly affected S-adenosylmethionine metabolism. The ratio of spermidine/spermine decreased markedly, but the concentration of total polyamines did not change significantly. The activity of S-adenosylmethionine decarboxylase initially decreased and then increased during prolonged starvation. This increase was dependent on intact adrenals. Re-feeding of starved animals caused a rapid but transient stimulation of polyamine synthesis and also increased the concentrations of S-adenosylmethionine and S-adenosylhomocysteine. Similarly, cortisol treatment enhanced the synthesis of polyamines, S-adenosylmethionine and S-adenosylhomocysteine. Feeding with a methionine-deficient diet for 7-14 days profoundly increased the concentration of spermidine, whereas the concentrations of total polyamines and of S-adenosylmethionine showed no significant changes. The results show that nutritional state and adrenal function play a significant role in the regulation of hepatic metabolism of S-adenosylmethionine and polyamines. They further indicate that under a variety of physiological and experimental conditions the concentrations of S-adenosylmethionine and of total polyamines remain fairly constant and that changes in polyamine metabolism are not primarily connected with changes in the accumulation of S-adenosylmethionine or S-adenosylhomocysteine.

Adenosylmethionine Decarboxylase↗
PubMed1977

Tissue distribution of S-adenosylmethionine and S-adenosylhomocysteine in the rat. Effect of age, sex and methionine administration on the metabolism of S-adenosylmethionine, S-adenosylhomocysteine and polyamines.

The tissue distribution of S-adenosylmethionine, S-adenosylhomocysteine, methionine adenosyltransferase and S-adenosylhomocysteine hydrolase was explored in the rat. Also the effects of methionine administration on the accumulation of S-adenosylmethionine, S-adenosylhomocysteine and polyamines were studied in rat liver, brain and kidney. The tissue distribution of S-adenosylmethionine, S-adenosylhomocysteine, methionine adenosyltransferase and S-adenosylhomocysteine hydrolase was similar in both sexes, and was only slightly changed with age. The specific activity of S-adenosylhomocysteine hydrolase greatly exceeded that of methionine adenosyltransferase, and the concentration of S-adenosylmethionine was higher than that of S-adenosylhomocysteine in all tissues examined. However, the hepatic S-adenosylmethionine/S-adenosylhomocysteine ratio was dependent on food supply and on the age of the animal. No correlation was noticed between the activity of methionine adenosyltransferase and the concentrations of the adenosyl compounds in different tissues. Intraperitoneal administration of methionine resulted in a profound but transient increase in the hepatic concentrations of S-adenosylmethionine and S-adenosylhomocysteine. The concentration of S-adenosylmethionine was elevated also in the brain during the first 2h after methionine injection. The rise of S-adenosylmethionine concentration after methionine treatment could be diminished by simultaneous glycine administration. The results support the view that the rate-limiting factor of S-adenosylmethionine synthesis is the tissue concentration of methionine. They further suggest that glycine N-methyltransferase may have a regulatory role in the utilization of S-adenosylmethionine in the liver.

Age Factors↗
PubMed1976

A new method for the assay of tissue. S-adenosylhomocysteine and S-adenosylmethione. Effect of pyridoxine deficiency on the metabolism of S-adenosylhomocysteine, S-adenosylmethionine and polyamines in rat liver.

The hepatic synthesis and accumulation of S-adenosylhomocysteine, S-adenosylmethionine and polyamines were studied in normal and vitamin B-6-deficient male albino rats. A method involving a single chromatography on a phosphocellulose column was developed for the determination of S-adenosylhomocysteine and S-adenosylmethionine from tissue samples. Feeding the rat with pyridoxine-deficient diet for 3 or 6 weeks resulted in a four- to five-fold increase in the concentration of S-adenosylhomocysteine, whereas that of S-adenosylmethionine was only slighly elevated. The concentration of putrescine was decreased to half, that of spermidine was somewhat decreased and that of spermine remained fairly constant. The activities of L-ornithine decarboxylase, S-adenosyl-L-methionine decarboxylase, L-methionine adenosyltransferase and S-adenosyl-L-homocysteine hydrolase were moderately increased. S-Adenosylmethionine decarboxylase showed no requirement for pyridoxal 5'-phosphate. The major effect of pyridoxine deficiency of S-adenosylmethionine metabolism seems to be a block in the utilization of S-adenosylhomocysteine, resulting in the accumulation of this metabolite to a concentration that may inhibit biological methylation reactions.

Adenosylmethionine Decarboxylase↗
PubMed1976

Synthesis of hepatic polyamines, ribonucleic acid and S-adenosylmethionine in normal and oestrogen-treated chicks.

1. The hepatic synthesis and accumulation of polyamines, RNA and S-adenosylmethionine were studied in normal and oestrogen-treated immature male chicks. 2. Ornithine decarboxylase activity in chick liver and in whole chick embryo homogenate was preferentially located in the soluble supernatant fraction. 3. In general the activities of the enzymes involved in the synthesis of polyamines and S-adenosylmethionine decreased with increasing age.

Adenosylmethionine Decarboxylase↗
PubMedDate not supplied

Polyamine excretion in depleted patients with gastrointestinal malignancy: effect of perioperative nutrition and tumor removal.

Polyamines, synthesized by all mammalian cells, are involved in protein and energy metabolism. We measured urinary excretion of polyamines, putrescine, spermidine, spermine, and their metabolites N1-acetylspermidine and N8-acetylspermidine, resting energy expenditure, and nitrogen excretion in 12 depleted patients with gastrointestinal malignancy during preoperative and postoperative parenteral nutrition and in 7 patients with multiple trauma receiving similar parenteral nutrition. During preoperative nutrition support, the excretion of putrescine (p less than .05) and total polyamines (p less than .01) increased by 420% and 60%, respectively. Increases in energy balance and resting energy expenditure during nutrition could entirely explain the observed changes in polyamine excretion. Preoperatively, the excretion of N1-acetylspermidine (p less than .05), N8-acetylspermidine (p less than .001) and total polyamines (p less than .05) was higher in patients with a surgically noncurable tumor than in those with a surgically curable tumor. The energy balance and resting energy expenditure could also explain the differences in polyamine excretion between patients with surgically curable and noncurable disease, excluding the increased N8-acetylspermidine. Postoperatively, the excretion of N8-acetylspermidine in patients with multiple trauma without malignancy and in patients with palliative operation was similar, and was higher than in patients with a totally resected malignancy (p less than .01). Our results suggest that the excretion of polyamines reflects the activity of energy metabolism in general and that polyamine excretion is not specific for any particular disease.

Adult↗
PubMedDate not supplied

Differential effects of sepsis and trauma on urinary excretion of polyamines.

Urinary excretion of polyamines increases in patients with trauma and infection. To separate the effect of infection from the general metabolic response to sepsis, we studied 7 patients with sepsis and 13 patients with multiple trauma in the intensive-care unit. Urinary excretion of total and free polyamines, putrescine, spermidine, spermine, and their metabolites N1-acetylspermidine (N1-AcSPD) and N8-acetylspermidine (N8-AcSPD), and energy and nitrogen balance were measured. The patients were randomized to receive either hypocaloric glucose alone or with amino acids for 2 days. The excretion of individual polyamines, except spermine, significantly exceeded normal values in both patient groups; the excretion of total polyamines was 530 and 323% higher than normal in patients with sepsis and trauma, respectively. The excretion of N1-AcSPD and total spermidine was 141 and 74% higher in patients with sepsis than in patients with trauma, respectively (p < 0.05), whereas the excretion of N8-AcSPD was equal in both patient groups. This was also reflected as a significantly increased urinary ratio of N1-AcSPD to N8-AcSPD in septic patients (6.37 +/- 1.61; mean +/- SE) compared with patients after injury (2.69 +/- 0.27, p < 0.01) or a healthy population (1.08 +/- 0.04, p < 0.001). Amino acid infusion had no effect on polyamine excretion. The mean energy balance was -17.0 +/- 1.1 and -19.1 +/- 1.1 kcal.kg-1.day-1, and the mean nitrogen balance was -0.17 +/- 0.03 and -0.15 +/- 0.02 g.kg-1.day-1 in patients with sepsis and trauma, respectively (NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗