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PubMed1979

Synthesis and content of polyamines in bloodstream Trypanosma brucei.

The sensitive dansyl procedure was used to detect putrescine and spermidine, but not spermine and cadaverine, in pleomorphic Trypanosoma brucei. The polyamines were synthesized in vitro from [3H]ornithine, [14C]arginine and [14C]methionine. Proline, agmatine, and citrulline, but not glutamine, glutamic or pyroglutamic acids, stimulated spermidine formation from [4C]methionine. Putrescine and sperimidine synthesis occurred rapidly from ornithine: putrescine synthesis peaked in 0.5 h, spermidine in 1 h. Trypanosoma brucei assimilated exogenous 14C-labeled putrescine, spermidine, and spermine; spermidine and spermine were taken up 5 times as rapidly as putrescine. Polyamine syntheses may therefore be a practical target for novel trypanocies.

Amino Acids↗
PubMed1978

Adrenal luteinizing hormone releasing hormone receptors.

Paraffin sections of mouse adrenals processed with antiserum to luteinizing hormone-releasing hormone (LHRH) in the unlabeled antibody enzyme method reveal moderate staining in the cytoplasm of cells of zona fasciculata and reticularis. The stain is intensified upon pretreatment of sections with LHRH. Pretreated sections processed with solid phase immunoabsorbed LHRH are unstained. Analogues of LHRH deficient in the C-terminal glycine amide inhibit staining, while analogues deficient in the N-terminal pyroglutamic acid have no effect. It is concluded that the adrenal contains receptors for a ligand resembling LHRH in receptor and immunoreactivity. The possibility is considered that the ligand may be an inhibitor of pineal origin.

Adrenal Cortex↗
PubMed1977

Inactivation of thyrotrophin releasing hormone by human and rat serum.

The inactivation of thyrotrophin releasing hormone (pGlu-His-Pro-NH2, TRH) and its deamidated analogue pGlu-His-Pro-OH (TRH-OH) in human and rat serum has been studied using specific radioimmunoassays. No difference was apparent between human and rat serum with regard to proteolytic activity towards TRH and TRH-OH. It was found that the inactivation of both peptides is a saturable process. The disappearance of TRH was clearly inhibited by TRH-OH, luteinizing hormone-releasing hormone and dithiothreitol. The suppressive action of these compounds was observed to be dependent on their concentration. Proline and EDTA showed little inhibiting activity. Proline amide and pyroglutamic acid left the reaction unaffected. In no single instance could any production of TRH-OH from TRH be demonstrated.

Animals↗
PubMed1979

[Effect of luliberin on the activities of mitochondrial respiratory enzymes].

Luliberin, a luteinizing hormone-releasing hormone, was shown to inhibit the respiratory enzymes of rat liver mitochondria and submitochondrial particles prepared from beef heart mitochondria. At the hormone concentration of 8.10(-6) M the NADH-oxidase activity of the submitochondrial particles was inhibited by 50%. The fragments of the hormone and its analogs and pyroglutamic acid, oxytocin and bradikinin possessed practically no inhibiting effects. In the case of submitochondrial particles the inhibition was only observed in the presence of Ca2+ and was significantly decreased after addition of bovine serum albumin and phospholipase inhibitors -- butacaine and dicaine. It is assumed that the effect of luliberin on the respiratory chain is mediated through mitochondrial phospholipase.

Animals↗
PubMed1976

Demonstration of pyroglutamylpeptidase and amidase activities toward thyrotropin-releasing hormone in hamster hypothalamus extracts.

Using a radioimmunoassay method for thyrotropin-releasing hormone, the presence of thyrotropin-releasing hormone-metabolizing activity in various hamster tissues was demonstrated. While there was substantial activity degrading thyrotropin-releasing hormone in hypothalamus, there was a notable absence of such activity in pituitary. The enzymatic activity in the hypothalamus was shown to be soluble and separable into two fractions. Analysis of the metabolic products formed by the two enzymes indicated that one possessed an amidase activity (less than Glu-His-Pro-NH2 leads to less than Glu-His-Pro) and the other possessed pyroglutamylpeptidase activity (less than Glu-His-Pro-NH2 leads to less than Glu+His-Pro-NH2). Other peptides containing NH2-terminal pyroglutamic acid or COOH-terminal amide groups did not block the hydrolysis of thyrotropin-releasing hormone, suggesting that the enzymes were specific. Some inhibitors preferentially blocked the activity of one or the other enzymes. Of possible biological significance is the observation that thyroid-stimulating hormone inhibited the amidase activity while hydrocortisone inhibited the pyroglutamylpeptidase activity.

Amidohydrolases↗
PubMed1975

Intermediates of the gamma-glutamyl cycle in mouse tissues. Influence of administration of amino acids on pyrrolidone carboxylate and gamma-glutamyl amino acids.

GAMMA-Glutamyl transpeptidase, gamma-glutamyl cyclotransferase, L-pyrrolidone carboxylate hydrolase, gamma-glutamylcysteine synthetase and glutathione synthetase, the enzymes of the gamma-glutamyl cycle, were found in mouse brain, liver and kidney. The activity of L-pyrrolidone carboxylate hydrolase was many times lower than the activities of the other enzymes, and thus the conversion of L-pyrrolidone carboxylate to L-glutamate is likely to be the rate-limiting step of the cycle. The specificity of gamma-glutamyl cyclotransferase from mouse tissues was similar to that from rat tissues. The concentration of pyrrolidone carboxylate and gamma-glutamyl amino acids, intermediates of the gamma-glutamyl cycle, was determined by a gas chromatographic procedure coupled with electron capture detection. Administration of L-2-aminobutyrate, an amino acid that is utilized as substrate in the reaction catalyzed by gamma-glutamylcysteine synthetase, led to a large accumulation of gamma-glutamyl-2-aminobutyrate and pyrrolidone carboxylate in mouse tissues. L-Methionine-RS-sulfoximine, an inhibitor of gamma-glutamylcysteine synthetase, abolished the increase in concentration of pyrrolidone carboxylate. No accumulation of pyrrolidone carboxylate was observed after L-cysteine. The separate administration of several protein amino acids had little effect on the concentration of pyrrolidone carboxylate; however formation of small amounts of the corresponding gamma-glutamyl derivatives (e.g. gamma-glutamylmethionine and gamma-glutamylphenylalanine) was detected. These intermediates are probably formed by transpeptidation between glutathione and the corresponding amino acid, catalyzed by gamma-glutamyl transpeptidase. The concentration of pyrrolidone carboxylate increased significantly after administration of a mixture containing all protein amino acids, the highest increase occurring in the kidney. The results suggest that two separate pathways for the formation of gamma-glutamyl amino acids and pyrrolidone carboxylate exist in vivo. One of these results from the function of gamma-glutamylcysteine synthetase in glutathione synthesis. The other pathway involves the amino-acid-dependent degradation of glutathione, mediatedby gamma-glutamyl transpeptidase. Only very small amounts of free intermediates are apparently derived from the latter pathway, suggesting that the gamma-glutamyl amino acids formed in this pathway are either enzyme-bound or are directly hydrolyzed to glutamate and free amino acid.

Amino Acids↗
PubMed1978

The metabolic fate of glutamine nitrogen in the perfused rat kidney.

The fate of glutamine amide and amino nitrogen was determined in the perfused rat kidney. There is a deficit of about 40% in the recovery of glutamine nitrogen and NH3 in the perfusion medium. After correction for the tissue conetent of glutamine, the remaining nitrogen was fully accounted for by small amounts of NH3, glutamate, aspartate and a compound that liberated glutamate on acid hydrolysis, probably 5-oxopyrrolidine-2-carboxylate (pyroglutamate). The latter accounted for 8% of the glutamine metabolized.

Animals↗
PubMed1979

Amino acid sequence of the aminoterminal segment of dermatosparactic calf-skin procollagen type I.

The N-terminal procollagen peptide of the pN alpha 1(I) chain from dermatosparactic calf skin contains 139 amino acid residues. For the determination of the amino acid sequence the procollagen peptide was treated with pyroglutamate aminopeptidase, protease from Staphylococcus aureus V8 and trypsin. The fragments obtained were separated by molecular sieve and ion-exchange chromatography and submitted to automated Edman degradation. The procollagen peptide consists of three segments, an N-terminal globular domain which contains all the cysteine residues and most of the hydrophobic residues present in the entire peptide, a triple helical part with a relatively high content of proline and hydroxyproline, and a short nonhelical region which forms the connection to the nonhelical region of the alpha 1(I) chain and which contains the proline-glutamine bond specifically split by the N-terminal procollagen peptidase during conversion of procollagen to collagen.

Amino Acid Sequence↗
PubMed1977

Chemistry and pharmacology of arginine pyroglutamate. Analysis of its effects on the CNS.

By studying the influence of the arginine pyroglutamate on the CNS its variations were evidenced which are clearly identifiable through the analysis of the interaction with molecules having either a depressive or excitatory action. In the case of pentobarbital the antagonistic effect of the compound on the general anaesthesia is very intense and is equally present even when medazepam and flurazepam are associated. Equally obvious is the antagonism with barbiturate in the case of spontaneous motility but much less so with the two benzodiazepines. As far as the specialized behaviour is concerned, arginine pyroglutamate does not alter the sound discrimination capacity (responses in Sdelta punished) at fixed intervals (F.I.) nor does it influence the learning of a sound discrimination (responses in Sdelta punished) at varied intervals (V.I.). The process of learning is instead moderately accelerated in the case of a temporal discrimination and of a conditioned avoidance response (CAR) in the shuttle-box. No effect was found when the same amino acids were introduced alone or in random association. The hypothesis is proposed that the phenomena described depend on the different pharmacokinetics of arginine pyroglutamate that ensures brain concentrations sufficient to block the activity of depressive compounds but is not capable of influencing in a significant way the spontaneous and specialized behaviour of normal animals.

Animals↗