Tryptophan Pyrrolase Activity Research Articles

The role of dietary protein in generating daily rhythms in rat liver tryptophan pyrrolase and tyrosine transaminase

Groups of rats exposed to light for 12 hr daily were given access to an 18% casein diet or to a protein-free diet at different times of day or night, and killed 24 hr later. Tryptophan pyrrolase activity rose significantly during the dark period (by 34%–67%) in all animals. Tyrosine transaminase activity, however, rose during the dark period (by 163%) only among those eating protein. In rats given access to a protein-containing chow diet in the afternoon following an overnight fast and killed 2 or 4 hr later, tryptophan pyrrolase activity did not increase after food consumption, but tyrosine transaminase activity rose by 120%–140%. If animals consumed chow for 12 hr/day, starting either at the onset of darkness or 6 hr later, the daily increases in tryptophan pyrrolase began several hours before animals were given access to food rather than after food ingestion, while the daily increases in tyrosine transaminase were always noted immediately after eating. These observations confirm findings which indicate that the cyclic ingestion of dietary protein is of major importance in generating the tyrosine transaminase rhythm, but is of little significance in producing the tryptophan pyrrolase rhythm. Variations in plasma tryptophan concentration did not correlate well with tryptophan pyrrolase activity in any group fed a diet containing protein; plasma tryptophan concentrations did not rise prior to the increases in tryptophan pyrrolase activity, nor did they fall after these increases. Hence, the normal daily rhythm in tryptophan pyrrolase activity apparently neither results from nor elicits the plasma tryptophan rhythm.

The mechanism of inhibition of rat liver tryptophan pyrrolase activity by 4-hydroxypyrazolo(3,4-d)pyrimidine (Allopurinol).

1. Allopurinol (4-hydroxypyrazolo[3,4-d]pyrimidine) selectively inhibits the apotryptophan pyrrolase activity in homogenates of rat liver in vitro and after intraperitoneal administration. The inhibition is abolished by an excess of haematin. The allopurinol metabolite alloxanthine has no effect on the pyrrolase activity in vitro or after administration. Allopurinol also inhibits the activation of the enzyme in vitro by ascorbate, ethanol plus NAD(+), NADH, hypoxanthine or xanthine. It is suggested that these agents cause the conversion of a latent form of the pyrrolase into the apoenzyme, and that xanthine oxidase is not involved in this process. 2. The raised total pyrrolase activity observed after the administration of cortisol, cyclic AMP, tryptophan, salicylate or ethanol is lowered by allopurinol in vitro to the corresponding holoenzyme values. A similar effect is observed when allopurinol is administered shortly before cortisol or cyclic AMP. Pretreatment of rats with allopurinol completely prevents the enhancement of the pyrrolase activities by tryptophan, salicylate or ethanol. 3. It is suggested that allopurinol inhibits rat liver tryptophan pyrrolase activity in vitro and after administration by preventing the conjugation of the apoenzyme with its haem activator. The possible usefulness of combined allopurinol-tryptophan therapy of affective disorders is discussed.

Antidepressants and liver tryptophan pyrrolase activity

Tricyclic antidepressants were found to diminish liver tryptophan pyrrolase activity in rats. Neuroleptics and anticholinergics, used for comparison, did not change the enzyme activity. No effects of imipramine were observed in vitro nor in adrenalectomized animals. Imipramine did not influence tryptophan or hydrocortisone induction of tryptophan pyrrolase. Antidepressants in doses which lower the enzyme activity also lowered blood plasma concentration of 11-hydroxycorticosteroids. This effect may be responsible for inhibition of tryptophan pyrrolase activity by antidepressants. Inhibitors of monoamine oxidase did not decrease liver tryptophan pyrrolase activity in rats and mice but suppressed tryptophan induction of this enzyme. The possible relations between reduction by antidepressants of liver tryptophan pyrrolase activity and enhanced serotonin synthesis in the central nervous system and the thymoanaleptic effect are discussed.

Influence of non-steroid anti-inflammatory and immunosuppressive drugs on hepatic tryptophan pyrrolase activity in rats

High oral doses of the anti-inflammatory drugs indomethacin, acetylsalicyclic acid, sodium salicylate, salicylamide, mefenamic acid, flufenamic acid, amidopyrine, phenylbutazone and benzydamine administered repeatedly, did not influence tryptophan pyrrolase activity in livers of intact rats. The nonresponsiveness of tryptophan pyrrolase was in contrast to a stimulation of tyrosine aminotransferase caused by flufenamic acid. Induction of tryptophan pyrrolase due to hydrocortisone was not inhibited generally by non-steroid drugs; exceptions were flufenamic acid and benzydamine which depressed hormonal induction. The authors' recent statement is confirmed that inhibition of protein synthesis due to induction is no essential property of non-steroid antiinflammatory drugs. The immunosuppressive drugs cyclophosphamide, triaziquone and azathioprine increased tryptophan pyrrolase activity, probably due to an inhibition of enzyme degradation; chloroquine, 6-mercaptopurin, 6-azauridin and amethopterin did not influence enzyme activity. Induction of tryptophan pyrrolase due to hydrocortisone was depressed by azathioprine, 6-mercaptopurin, 6-azauridin and amethopterin.

Effect of chronic lithium treatment on monoamine metabolism in rat brain.

Lithium chloride was administered chronically in two dose levels to rats giving serum lithium concentrations of about 0.4 and 0.7 meq/l. Treatment with the lower lithium dose did not affect monoamine metabolism in the brain. With the higher dose, accumulation of labelled 5-HT and 5-HIAA in the brain during intravenous infusion of 3H-tryptophan was increased. The effect was also present in the spinal cord following transection of 5-HT neurons, thus occurring independently of nerve impulse activity. The disappearance of labelled 5-HT from brain after intravenous injection of 3H-tryptophan was reduced in lithium-treated animals, indicating that lithium diminishes release of 5-HT from its storage sites. Brain tryptophan was augmented by lithium, whereas levels of free and total tryptophan in serum as well as its catabolism, reflected by liver tryptophan pyrrolase activity, were unaltered. Accumulation and disappearance of labelled dopamine and noradrenaline formed from 14C-tyrosine in brain were not changed by lithium treatment. It is concluded that chronic treatment of rats with lithium within the low dose range recommended for man affects 5-HT, but not catecholamine synthesis and turnover in brain.

Tryptophan to niacin pathway in scleroderma and in dermatomyositis.

Nine cases of scleroderma (systemic sclerosis 7, morphea 2) and 4 cases of dermatomyositis, all in the active phase, were examined. An alteration of the hepatic kynureninase activity was constantly observed. This enzymatic damage was confirmed by the direct determination on the liver in scleroderma but it was not accompanied either by an increase of the tryptophanpyrrolase activity or by histamine fast achlorhydria. The results are discussed.

Effect of cannabis extract, Δ 9-tetrahydrocannabinol and lysergic acid diethylamide on rat liver enzymes

The effect of intraperitoneal administration of cannabis extract, Δ 9-tetrahydrocannabinol (THC) and lysergic acid diethylamide (LSD), both at high (50 mg/kg, 100 mg/kg and 100 μg/kg respectively) and low (10 mg/kg, 10 mg/kg and 10 μg/kg respectively) doses, on the rat liver tyrosine α-ketoglutarate transaminase and tryptophan pyrrolase activity was studied and found that cannabis extract and Δ 9-tetrahydrocannabinol, but not LSD, increased the above two enzyme activities after 6 hr of injection.

Effect of chlorpromazine on induction of different hepatic enzymes

Following a single high dose of intraperitoneal administration of chlorpromazine (50 mg/kg) into adult male albino rats, tyrosine-α-ketoglutarate transaminase (TKT) and tryptophan pyrrolase (TP) activity of rat liver are increased near about 3-fold within 5 hr whereas threonine dehydrase (TD) activity increases maximally within 2 hr. Actinomycin D (Act. D) inhibits the chlorpromazine induced stimulation of all the three enzymes.

The effect of staphylococcal α-toxin on rat liver tryptophan pyrrolase and uridine kinase

The administration of crude staphylococcal α-toxin increased the tryptophan pyrrolase activity in the liver of intact rats. The elevation did not occur in adrenalectomized or hypophysectomized animals. The level of uridine kinase was also raised after toxin administration, both in adrenalectomized and hypophysectomized animals but with a different time-course. The enhancement of uridine kinase and its time-dependency was similar after hydrocortisone administration. Actinomycin d which inhibits induction of tryptophan pyrrolase did not substantially influence the enhancement of uridine kinase activity after hydrocortisone. Twenty-two and 46 hr after staphylotoxin administration the level of uridine kinase was still enhanced. The same effect was observed after the administration of inhibitors of protein synthesis.

Tryptophan pyrrolase in the liver of guinea pig: The absence of hydrocortisone induction

The adaptive response of liver tryptophan pyrrolase ( l-tryptophan: oxygen oxidoreductase, EC 1.13.1.12) of guinea pig to hormone and substrate treatment was investigated and the results compared with similar studies on other species. Tryptophan treatment caused a marked increase in the tryptophan pyrrolase activity, and this increase was only slightly inhibited by actinomycin D. The administration of glucocorticoids increased the incorporation of [ 3H]uridine into ribonucleic acid of guinea pig liver (and decreased that into ribonucleic acid of guinea pig thymocytes), but it failed to induce tryptophan pyrrolase. Two forms of tryptophan pyrrolase (oxidized and reduced forms) were demonstrated in the soluble fraction of liver homogenate from guinea pig.

Further Studies on the Effect of Dietary Carbohydrate and Fat on Protein Metabolism in Rats

A systematic experiment has been carried out in attempting to elucidate the biochemical mechanism underlying “protein sparing” action of dietary carbohydrate and fat. A more simplified experimental condition was employed in the present investigation in comparison with that in our previous experimental design; the effect of dietary carbohydrate and fat on the body protein metabolism was examined in the absence of any protein in the diet. Feeding of either carbohydrate or fat caused a marked decrease in the level of urinary nitrogen and urea. The ingestion of either carbohydrate or fat by rats resulted in a reduction of the rate of ureogenesis in the rat liver with the concomitant decrease in the activities of hepatic amino acid-catabolizing enzymes, e.g., threonine dehydratase, tryptophan pyrrolase, arginase, glutamic-pyruvic transaminase, glutamic-oxalacetic transaminase and glutamic dehydrogenase (except in fat-fed animals). The feeding of either carbohydrate or fat did not result in changes in the level of free amino nitrogen in blood, indicating that the supply of amino acid may not exert an important role in the ureogenesis in liver. The overall results indicate that the reduction of the activities of hepatic amino acid-catabolizing enzymes elicited by the feeding of either carbohydrate or fat may govern protein metabolism in the rat body.

Changes in liver tryptophan and tryptophan pyrrolase activity after administration of salicylate and tryptophan to the rat

The tryptophan content and tryptophan pyrrolase activity of rat liver were measured after the intraperitoneal administration of a range of doses of l-tryptophan and salicylate. The injection of salicylate increased both the total and the free concentration of tryptophan in the liver. It is suggested that salicylate induces tryptophan pyrrolase by releasing tryptophan from its binding sites on serum and liver proteins.

Studies on the genetic control of tryptophan pyrrolase in Drosophila melanogaster.

A reexamination of the role of the vermilion cistron (v: 1–33.0) in the control of tryptophan pyrrolase in Drosophila melanogaster uncovered several, previously unknown features about this enzyme: 1. Crude extracts of Drosophila possess one or more inhibitors which may be removed by Norit treatment during homogenization. 2. Contrary to previous assertion, crude wild type extracts are stimulated by an exogenous source of hematin, and upon purification, become heavily dependent upon added methemoglobin. 3. The wild type enzyme exhibits a lag period in time course of product accumulation which is eliminated by preincubation with methemoglobin and α-methyltryptophan. 4. The molecular weight of the wild type enzyme is estimated at approximately 150000 Daltons. 5. A linear increase of tryptophan pyrrolase activity as a function of dosage of v+ alleles supports the contention that the vermilion cistron is the structural gene for this enzyme. 6. A sex difference in response to gene dosage (dosage compensation) is seen.

The effects of salicylate on the activity of rat liver tryptophan pyrrolase in vitro and in vivo

1. Salicylate, in concentrations of 0.05mm and above, inhibits the basal activity of tryptophan pyrrolase in homogenates of rat liver and the activity induced by cortisol but not that induced by tryptophan. The inhibition is abolished by adding haematin to the reaction mixtures. 2. The intraperitoneal injection of 400mg of sodium salicylate/kg in the rat causes a decrease in the tryptophan pyrrolase activity in the liver at 30min, the activity is restored to normal at 2h, increases to sixfold after 5h and returns to the basal value at 12h. The activation of the enzyme by salicylate is prevented by the administration of cycloheximide but not by pretreatment with actinomycin D. The effects of the combined injection of salicylate and cortisol are additive, whereas those of salicylate plus tryptophan are not. The injection of salicylate causes a progressive increase in the holo-/apo-enzyme ratio and an increased content of tryptophan in the liver over a period of 3h. 3. It is suggested that salicylate inhibits tryptophan pyrrolase activity in vitro and in vivo by interacting with iron protoporphyrins and causes a later enhancement of the enzyme activity in vivo by a mechanism involving the release of tryptophan from its binding sites on circulating albumin and on other proteins.

Tryptophan pyrrolase activity during development in mosquito (Culex pipiens)

1.1. Studies on tryptophan pyrrolase activity during development in Culex pipiens showed that the specific activity of the enzyme was about 2·5 times higher in larvae and adults than in pupae.2.2. The mosquito enzyme differed from the rat liver enzyme with respect to its activation by methemoglobin and ascorbic acid.3.3. The results showed that the prosthetic group (heme) was more tightly bound to the mosquito enzyme than to the rat liver enzyme.

Cytoplasmic changes during thioacetamide induced hepatocarcinogenesis in rats.

Cytoplasmic changes were investigated in livers of rats at various intervals up to 50 weeks during primary induction of hepatoma by thioacetamide feeding.Microsomal Glucose-6-phosphatase and ATPase activities were shown to decrease progressively with increased period of thioacetamide feeding the fall in activities being more pronounced during the first 15 weeks.Hormonal induction of tryptophan pyrrolase and tyrosine transaminase activities was shown to undergo a significant decrease of 65% and 55% respectively at the end of 50 weeks feeding.The substrate induced tryptophan pyrrolase activity was decreased to 50% during the 50 weeks period whereas the substrate induced tyrosine transaminase activity gradually increased to 200%. The latter is attributable to differences in the optimal induction dose of tyrosine in normal and carcinogen fed rats.The m-RNA template lifetime for tryptophan pyrrolase was shown to be exceeding 24 hours in normal rats as against that of 13 hours in rats fed with carcinogen for 30 weeks. On the other hand the m-RNA template lifetime for tyrosine transaminase was 3 hours in control rats while it was 7 hours in the carcinogen fed rats.The observed changes were shown to occur long before the onset of malignant transformation.The alterations in terms of decreased Glucose-6-phosphatase and substrate induced tryptophan pyrrolase activities were shown to be reversible when the carcinogen was withdrawn from the diet after 30 weeks of feeding.The significance of these observations is discussed in relation to damage to endoplasmic reticulum during hepatocarcinogenesis.

The effects of salicylate of the activity of tryptophan pyrrolase in rat liver.

The effects of salicylate of the activity of tryptophan pyrrolase in rat liver.

Activation of liver tryptophan pyrrolase of rat by isocarboxazid in vivo.

Activation of liver tryptophan pyrrolase of rat by isocarboxazid in vivo.

EXCRETION OF KYNURENIC ACID AND XANTHURENIC ACID DURING INFECTION

Urinary excretion of diazotizable amines in acute febrile disease was demonstrated 90 years ago. These substances were subsequently identified as metabolites of tryptophan via the kynurenine pathway and the hepatic enzyme tryptophan pyrrolase (TP) was established as a regulator of this pathway. Animal studies have previously shown that TP has a circadian periodicity of activity and can be induced by gram-negative infections in the intact animal. Steroid administration also can enhance TP activity whereas endotoxin inhibits TP. This study measured urinary excretion of kynurenic acid (KA) and xanthurenic acid (XA), two tryptophan metabolites via the kynurenine pathway, in 26 hospitalized children with a variety of febrile disorders and 10 age-matched control subjects. Increased excretion of these metabolites was noted in the febrile patients and was unrelated to etiology of the fever. Circadian periodicity in the excretion of these metabolites was observed in both normal and febrile individuals. Significant group periodicity was not noted for minimal and maximal excretory values did not occur synchronously in patients within any group. Two patients with endotoxic shock failed to exhibit an increased excretion of kynuremic acid and xanthurenic acid presumably because of inhibition of TP. A biochemical basis for the therapeutic use of exogenous corticosteroids in endotoxic shock is postulated.

Tryptophan catabolism during sporulation in Bacillus cereus.

1. Two intermediates of tryptophan catabolism were isolated from a sporulating culture of Bacillus cereus and identified as anthranilic acid and kynurenine by their spectral properties. 2. During sporulation the rate of formation of anthranilic acid and kynurenine by whole cells increased and reached a maximum at the pre-spore stage. 3. The specific activities of tryptophan pyrrolase and formylase also increased during sporulation and exhibited a maximal activity at the pre-spore stage. 4. Kynureninase activity reached a maximum during early stages of sporulation and then started to decline. 5. There was a net increase in the activity of tryptophan pyrrolase when cells were grown in the presence of l-tryptophan or dl-kynurenine. 6. The cultures exhibited the maximal activity of kynureninase 2h earlier in the presence of dl-kynurenine whereas l-tryptophan delayed the appearance of the maximal activity by 2h. 7. The omission of glucose from the medium had no effect on the pattern of development of tryptophan pyrrolase during growth and sporulation. 8. On the addition of tryptophan to a chemically defined medium no significant change in the pattern of development of tryptophan pyrrolase was observed.