Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:6.3.5.5 (CPS)
 1,262 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The submitochondrial localization of the four mitochondrial enzymes associated with urea synthesis in liver of Squalus acanthias (spiny dogfish), a representative elasmobranch, was determined. Glutamine- and acetylglutamate-dependent carbamoyl-phosphate synthetase, ornithine carbamoyltransferase, glutamine synthetase, and arginase were all localized within the matrix of liver mitochondria. The subcellular and submitochondrial localization and activities of several related enzymes involved in nitrogen metabolism and gluconeogenesis in liver and dogfish are also reported. Pyruvate carboxylase and phosphoenolpyruvate carboxykinase were localized in the mitochondrial matrix. Synthesis of citrulline by isolated mitochondria from ornithine proceeds at a near optimal rate at ornithine concentrations as low as 0.08 mM. The same stoichiometry and rates of citrulline synthesis are observed when ornithine is replaced by arginine. The mitochondrial location of arginase does not appear to reflect a mechanism for regulating ornithine availability.
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PMID:Submitochondrial localization of arginase and other enzymes associated with urea synthesis and nitrogen metabolism, in liver of Squalus acanthias. 286 47

N-Acetyl-L-glutamate synthetase (EC 2.3.1.1) catalyses the synthesis of N-acetyl-L-glutamate, an allosteric activator of carbamoyl-phosphate synthetase I in the liver of ureotelic animals, and the first enzyme is activated specifically by arginine. We have proposed that arginine can stimulate acetylglutamine synthetase in vivo and thereby increase the mitochondrial content of acetylglutamate. The effects of arginine on acetylglutamate synthesis in isolated mitochondria were investigated in detail in the present work. When rat liver mitochondria were isolated and incubated with [14C]glutamate and unlabelled acetate as substrates, acetyl[14C]glutamate synthesis in the mitochondria was more extensive in the presence than in the absence of L-arginine. There was no significant difference between the specific radioactivities of intramitochondrial [14C]glutamate in the presence and absence of arginine. When rat liver mitochondria were incubated with [14C]acetate and unlabelled glutamate as substrates, arginine also stimulated acetyl[14C]glutamate synthesis in the isolated mitochondria. L-Lysine or L-homoarginine, which does not activate acetylglutamate synthetase, had no effect on acetylglutamate synthesis, in the isolated mitochondria. The arginine concentration giving half-maximal synthesis of acetylglutamate in isolated mitochondria was about 50 microM, which is in the range of physiological concentrations of arginine in the liver. As we previously reported [Kawamoto, Ishida, Mori & Tatibana (1982) Eur. J. Biochem. 123, 637-641], the sensitivity of acetylglutamate synthetase to arginine activation undergoes marked changes after food ingestion. The extent of arginine activation of acetylglutamate synthesis in isolated mitochondria correlated well with the sensitivity of acetylglutamate synthetase extracted from the mitochondria to arginine activation. These data lend further support to the idea that arginine itself activates the mitochondrial synthesis of acetylglutamate.
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PMID:Stimulatory effect of arginine on acetylglutamate synthesis in isolated mitochondria of mouse and rat liver. 286 9

Neurospora crassa contains two carbamoyl-phosphate synthetases: a mitochondrial enzyme (CPS-A) which supplies carbamoyl phosphate for arginine biosynthesis, and a nuclear enzyme whose product is used for the synthesis of pyrimidines. We have prepared antiserum against a highly purified preparation of the large subunit of CPS-A and have used the antiserum to demonstrate that the large subunit is, like most mitochondrially localized proteins, initially synthesized as a higher molecular weight precursor. The CPS-A antiserum cross-reacts with the nuclear enzyme, allowing us to identify the product of the complex N. crassa pyr-3 genetic locus as a protein with a subunit molecular weight of 180,000. Finally, we have found that the CPS-A antiserum also cross-reacts with carbamoyl-phosphate synthetases from bacteria, yeast, and mammals. The immunological relatedness of carbamoyl-phosphate synthetases from such diverse species suggests that the protein sequences required for carbamoyl phosphate production have been highly conserved during the course of evolution.
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PMID:Carbamoyl-phosphate synthetases from Neurospora crassa. Immunological relatedness of the enzymes from Neurospora, bacteria, yeast, and mammals. 293 45

Citrulline is synthesized in mitochondria of Neurospora crassa from ornithine and carbamoyl phosphate. In mycelia grown in minimal medium, carbamoyl phosphate limits citrulline (and arginine) synthesis. Addition of arginine to such cultures reduces the availability of intramitochondrial ornithine, and ornithine then limits citrulline synthesis. We have found that for some time after addition of excess arginine, carbamoyl phosphate synthesis continued. Very little of this carbamoyl phosphate escaped the mitochondrion to be used in the pyrimidine pathway in the nucleus. Instead, mitochondrial carbamoyl phosphate accumulated over 40-fold and turned over rapidly. This was true in ornithine- or ornithine carbamoyltransferase-deficient mutants and in normal mycelia during feedback inhibition of ornithine synthesis. The data suggest that the rate of carbamoyl phosphate synthesis is dependent to a large extent upon the specific activity of the slowly and incompletely repressible synthetic enzyme, carbamoyl-phosphate synthetase A. In keeping with this conclusion, we found that when carbamoyl-phosphate synthetase A was repressed 2-10-fold by growth of mycelia in arginine, carbamoyl phosphate was still synthesized in excess of that used for residual citrulline synthesis. Again, only a small fraction of the excess carbamoyl phosphate could be accounted for by diversion to the pyrimidine pathway. The continued synthesis and turnover of carbamoyl phosphate in mitochondria of arginine-grown cells may allow rapid resumption of citrulline formation after external arginine disappears and no longer exerts negative control on ornithine biosynthesis.
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PMID:Arginine-specific carbamoyl phosphate metabolism in mitochondria of Neurospora crassa. Channeling and control by arginine. 295 16

Yeast URA2 encodes a multifunctional carbamoyl phosphate synthetase-aspartate transcarbamylase of 220,000 molecular weight. We determined the nucleotide sequence of the 5' proximal part of the gene which is responsible for the glutamine amide transfer function of the carbamoyl phosphate synthetase activity. Alignment of the enzyme sequence derived from URA2 with sequences from Escherichia coli carA carB and yeast arginine-specific CP A1 CP A2 indicates that monofunctional and bifunctional carbamoyl phosphate synthetases are probably homologous. The URA2-derived enzyme organization is NH2-carbamoyl phosphate synthetase-aspartate transcarbamylase-CO2H.
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PMID:Nucleotide sequence of the pyrimidine specific carbamoyl phosphate synthetase, a part of the yeast multifunctional protein encoded by the URA2 gene. 303 94

The carAB operon, encoding carbamoylphosphate synthetase (CPSase; EC 6.3.5.5) is transcribed from two tandem promoters. The upstream promoter (P1) is controlled by pyrimidines and the downstream promoter (P2) is controlled by arginine. We have isolated a new type of constitutive mutation (carP) that specifically affects the control of the pyrimidine-sensitive promoter but does not appear to influence other genes of the pyrimidine pathway. The carP mutation acts in trans and is dominant, which suggests that the carP product is an activator of car transcription. The downstream promoter P2, which is repressed by arginine, overlaps two operator modules characteristic of the arginine regulon. We have isolated two operator-constitutive mutations that specifically affect P2; both map in the upstream ARG box at a strongly conserved position.
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PMID:carP, a novel gene regulating the transcription of the carbamoylphosphate synthetase operon of Escherichia coli. 306 18

The expression of gene CPA1, encoding the glutaminase subunit of the arginine pathway carbamoyl-phosphate synthetase, is repressed by arginine at a posttranscriptional level. The 5' region of CPA1 mRNA contains a 25 codon upstream open reading frame. The importance of this feature for the repression of CPA1 expression has been analyzed by oligonucleotide-directed mutagenesis and by sequencing of constitutive cis-dominant mutations obtained in vivo. The results show that the leader peptide, the product of the upstream open reading frame, plays an essential, negative role in the specific repression of CPA1 by arginine. A model of translational regulation of CPA1 is proposed that takes into account the cis-dominance of the mutations affecting the leader peptide.
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PMID:The leader peptide of yeast gene CPA1 is essential for the translational repression of its expression. 355 44

We have confirmed that arginine-deficient diets increase the liver activities (units per 100 g) of the first four arginine biosynthetic enzymes of the urea cycle in Wistar rats, but not the activity of arginase. In contrast, rat liver cells cultured in monolayers for 48, 72 or 96 h in arginine-free L-15 or minimum essential medium showed no changes in carbamoyl-phosphate synthase (EC 6.3.4.16), ornithine transcarbamylase (EC 2.1.3.3), argininosuccinate synthase (EC 6.3.4.5), argininosuccinase (EC 4.3.2.1) or arginase (EC 3.5.3.1) activities. The arginine content of the cells grown on deficient medium was 36% of that of cells grown on 2.9 mM arginine-sufficient L-15, yet the urea excretion rate into the medium was reduced to 7% of the rate in control cells and the excretion of orotic acid was 400% of that in control cells. A Morris rat hepatoma cell line, 7800C1, which maintains activities of all five urea cycle enzymes, showed no consistent increases in the activities of the first four enzymes when the arginine in the medium was varied between 0 and 2 mM. Thus, in spite of severe arginine deficiency, cultured rat liver cells and hepatoma cells do not show the derepression-like response seen by other investigators when nonliver cells were cultured in arginine-deficient media. The difference between in vivo and in vitro effects of arginine deficiency on urea cycle activities remains unexplained.
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PMID:Differing effects of arginine deficiency on the urea cycle enzymes of rat liver, cultured hepatocytes and hepatoma cells. 368 73

The urea biosynthetic pathway functions in mammalian liver to convert excess ammonia to urea and to maintain the concentration of ammonia in blood at nontoxic levels. This action is accomplished by enzymatic adaptation to quantitative changes in dietary protein. The first two enzymes of the pathway are found in the intestine of the adult mouse, but they do not adapt to dietary change. The enzymes in the intestine produce citrulline, which is carried by the bloodstream to the kidney, where it is converted by the next two enzymes of the pathway to arginine. This mechanism serves as the major source of circulating arginine. We have demonstrated that, at birth, the arginine-synthesizing enzymes in the kidney of the C57Bl/6 mouse are minimally developed, whereas in the intestine activity of carbamoyl-phosphate synthase is elevated and argininosuccinate synthase and lyase, usually present only in trace quantities in the adult intestine, are markedly increased in the newborn. The arginine formed cannot be converted to urea, since arginase does not appear in intestinal cells of the mouse until the age of 15 days. Except for liver, intestine has the most rapid protein turnover of any normal tissue. Our study indicates that, at a time when no other endogenous source of arginine for protein synthesis is available, the intestine of the newborn C57Bl mouse is capable of synthesizing arginine from either citrulline or NH3 and CO2.
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PMID:Development of arginine-synthesizing enzymes in mouse intestine. 372 68

Studies were conducted to determine whether rainbow trout fingerlings possess the ability to synthesize arginine via the urea cycle. Several urea cycle enzymes were detected in trout tissues. An experiment was conducted to determine whether the enzymes increase in response to starvation or in response to dietary protein level (0, 30, 40, 50% protein). Although some effects were observed, they did not appear to be consistent with the function of the urea cycle as a mechanism of detoxifying ammonia in the fish. The activities of kidney arginase and liver and muscle carbamoyl phosphate synthetase (CPS) were higher (P less than 0.05) when protein was omitted from the diet (P less than 0.05) than when it was present but were unaffected by protein level otherwise. The activities of liver arginase and kidney and muscle CPS and ornithine transcarbamoylase (OTC) were higher (P less than 0.05) in starved fish than in fish that received adequate levels of protein. Liver CPS and OTC were lower in starved fish than in fish fed 30% protein. L-[l-14C]ornithine hydrochloride and L-[carbamoyl-14C]citrulline, injected intraperitoneally, were incorporated into tissue arginine, a finding consistent with arginine biosynthesis via the urea cycle. When one-half of dietary arginine was replaced by equimolar amounts of glutamic acid, ornithine or citrulline, glutamic acid markedly reduced growth (P less than 0.05), whereas growth was depressed only slightly by ornithine (P less than 0.05) and not depressed by citrulline (P greater than 0.05). We conclude that trout have a urea cycle that provides for potential arginine biosynthesis.
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PMID:Urea cycle activity and arginine formation in rainbow trout (Salmo gairdneri) 376 Oct 21


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