Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rat hepatoma cells that do not synthesize the hepatic enzyme ornithine carbamoyl transferase spontaneously give rise to producing cells at a low frequency. Reexpression of this differentiation trait is strongly increased by 5-azacytidine treatment, suggesting that hypermethylation plays a critical role in the impaired expression of the ornithine carbamoyl transferase gene in hepatoma cells.
Mol Cell Biol 1984 Apr
PMID:Spontaneous and 5-azacytidine-induced reexpression of ornithine carbamoyl transferase in hepatoma cells. 620 23

Arginine is rapidly depleted from the medium during the cultivation of T. vaginalis in a defined or semi-defined medium. It is broken down to ornithine, ammonia and carbon dioxide by the three enzymes of the dihydrolase pathway: arginine deiminase, catabolic ornithine carbamyltransferase (OCTase) and carbamate kinase. Arginase and urease as well as citrulline hydrolase appear to be absent. Ornithine, a product of the pathway was further converted to putrescine by an active ornithine decarboxylase. Apparent substrate Km values determined were arginine deiminase, 103 microM; catabolic OCTase, 71 microM; ornithine decarboxylase 134 microM. A substrate level phosphorylation is associated with the pathway; the significance of this to the overall energy economy of the cell is unclear.
Mol Biochem Parasitol 1983 Jul
PMID:The pathway of arginine catabolism in the parasitic flagellate Trichomonas vaginalis. 631 11

An arginase isolated from a capsulated Bacillus anthracis strain was highly purified and crystallized. The chemical and immunological characteristics of this enzyme re described. Some very important properties differ from those of another bacterial arginase, i.e. Staphylococcus aureus arginase, described in a previous paper (Soru et al. (2)). The two arginases have different crystallization forms, different molecular weight, Km, thermostability, Arrhenius activation energy. They have another N-terminal group and are immunologically strictly specific. These differences point to distinct proteins. The fact that two arginases of different origin are structurally non-identical suggests that they may be involved in different metabolic processes. Staphylococcal arginase was shown to participate in a complete ureogenetic cycle, for it also possesses the other enzymes of the cycle (Soru et al. (2)). Except arginase, no other enzyme of this cycle was identified in the capsulated B. anthracis strain. Arginase may be involved in another metabolic pathway, one that is important for the strain, such as the synthesis of glutamic acid, since the capsular material of the strain is a polymer gamma-linked polyglutamic acid, mainly configuration D (Ivanovic and Bruckner (20)). The fact that the N-terminal residue of B. anthracis arginase is a tetramer containing glutamic acid together with proline (in addition to alanine and glycine) suggests that arginase may participate as a regulatory enzyme in the synthesis of glutamic acid from proline via ornithine and arginine, respectively. This pathway is found in many bacteria. The proline oxidase system, which is supposed to catalyse the conversion of proline to glutamic acid, is under study now in Bacillus anthracis strains.
Mol Cell Biochem 1983
PMID:Chemical and immunological properties of B. anthracis arginase and its metabolic involvement. 640 30

Ornithine decarboxylase activity in mouse liver is predominantly located in the cell nuclei. After injection of some inducing agents (thioacetamide, diethylnitrosamine, hydrocortisone) the enzyme leaves the nucleus for cytosol. A circadian rhythm of ornithine decarboxylase activity has been observed in nucleus and cytosol, the decrease of enzyme activity in the nucleus being accompanied by its increase in cytosol. The enzyme obtained from intact mice with a minimal level of ornithine decarboxylase activity in the cytosol differs in ion-exchange properties, pH-optimum and Km for ornithine from the thioacetamide stimulated (nucleus enzyme).
Mol Biol (Mosk)
PMID:[Two variants of ornithine decarboxylase activity in the mouse liver. The nature of enzyme induction]. 654 Aug 39

The genetic regulation of enzymes involved in arginine and ornithine synthesis has been investigated in the parasitic trypanosomatid Herpetomonas samuelpessoai. The activities of two enzymes involved in arginine synthesis, ornithine carbamoyltransferase (OCTase) and argininosuccinate lyase (ASLase) were depressed whereas the enzyme citrulline hydrolase (CHase), which is involved in ornithine synthesis, was increased in arginine supplemented cultures of the parasites. The depression of OCTase activity in the presence of arginine was not due to feedback inhibition and CHase activity of uninduced cultures was not enhanced by exogeneous arginine. Studies of the kinetics of OCTase induction and repression revealed that arginine blocks OCTase synthesis but does not cause destruction of the enzyme. Ornithine, but not citrulline was found to counteract the arginine mediated repression of OCTase. Two classes of canavanine resistant mutants of H. samuelpessoai were isolated. One class was defective in arginine uptake whereas the other was affected in regulation of OCTase and ASLase which appear to be under coordinate control in H. samuelpessoai.
Mol Gen Genet 1983
PMID:Regulation of enzymes involved in ornithine/arginine metabolism in the parasitic trypanosomatid Herpetomonas samuelpessoai. 657 20

The nopaline catabolism (noc) genes are located in a 14.4 kb region on the pTiC58 plasmid of A. tumefaciens C58. These genes permit the bacterium to grow on nopaline N2-(1,3-dicarboxylpropyl) arginine, a substrate produced in plant tumors initiated by strain C58. The functions of the noc genes include the use of nopaline and L-ornithine as sole carbon and nitrogen sources. Using Tn5 insertional mutants, we have identified and mapped the positions of the genes that are responsible for nopaline catabolism (NopC), ornithine catabolism (OrnC) and nopaline uptake (NopU). A polar relationship was found between these phenotypes, which extended leftward over the noc region to the T-region. The NopC mutants were also deficient in nopaline oxidase, an enzyme that liberates free arginine from nopaline. The noc region also encodes the synthesis of a periplasmic protein, n1 that was induced by nopaline. Tn5 insertional mutations and molecular cloning were used to map the n1 production locus. The recombinant plasmids, pSa4480 and pSa4481, containing the 8.9 kb right-hand end of the noc region, conferred n1 production when introduced into a pTi-free strain of A. tumefaciens. Production of n1 by the strains carrying these plasmids required nopaline induction. We have identified in toto three noc loci: nocB, nocC, and nocA, which confer n1 production, nopaline oxidase production and ornithine catabolism respectively. A model is proposed whereby the noc genes of pTiC58 are contained on a leftward reading operon in the order nocB, nocC, and nocA.
Mol Gen Genet 1983
PMID:A functional map of the nopaline catabolism genes on the Ti plasmid of Agrobacterium tumefaciens C58. 657 60

We present here the results of investigations conducted by ourselves and others on the regulation of the expression of genes encoding the enzymes of the mammalian urea cycle as manifest in cultured cells of both hepatic and extrahepatic origin. Upon consideration of the recently discovered discrete non-hepatic arginase genetic locus in man and our consequent hypothesis that the form of arginase thus transcribed in such extrahepatic cells functions principally in providing ornithine for protein anabolism and polyamine biosynthesis, rather than in detoxifying ammonia through urea formation, we have chosen instead to study permanent cell lines that are derived from liver and continue to perform a variety of hepatic functions in culture as experimental models for probing the molecular mechanisms underlying the control of ureagenesis within the mature liver cell. Of two such arginase-positive rat-hepatoma lines, we have characterized extensively in one (H4-II-E-C3) the mode of action of glucocorticoids in augmenting the cellular levels of this enzyme as well as of argininosuccinate synthetase. To this end, we have recently demonstrated that these stimulations are both mediated by binding of the hormones to classical cytoplasmic steroid receptors in a specific and saturable fashion and have thus concluded that the H4-II-E-C3 line will provide a suitable cell culture system for subsequent more detailed experiments from which the information garnered will continue to be relevant to the ureagenic pathway as modulated in the differentiated hepatocyte in vivo.
Mol Cell Biochem 1983
PMID:Regulation of expression of genes for enzymes of the mammalian urea cycle in permanent cell-culture lines of hepatic and non-hepatic origin. 662 18

This study analyzes the effects of polyamine starvation on cell cycle traverse of an arginase-deficient CHO cell variant (CHO-A7). These cells grow well in serum-free medium, provided that it contains ornithine or polyamines or both. In the absence of ornithine or polyamines or both, the CHO-A7 cells develop severe polyamine deficiency and, as a consequence, grow more slowly. When grown to a stationary phase in the presence of ornithine or putrescine or both, the CHO-A7 cells became arrested in G0/early G1. However, when starved for ornithine and polyamines, they accumulated in the S and G2 phases. Ornithine and polyamine starvation of CHO-A7 cells causes an increase in ornithine decarboxylase activity. When this increase was prevented by treatment with DL-alpha-difluoromethylornithine, an enzyme-activated irreversible inhibitor of ornithine decarboxylase, growth was further suppressed, and a greater fraction of cells were found in the S and G2 phases of the cell cycle.
Mol Cell Biol 1984 May
PMID:Polyamine starvation prolongs the S and G2 phases of polyamine-dependent (arginase-deficient) CHO cells. 672 73

The effect of a single tube feeding of L-tryptophan on hepatic ornithine decarboxylase (ODC) activity in rats was investigated. The levels of ODC activity in the livers of control and experimental rats were assayed in vitro by measuring the release of 14CO2 from DL-[1-14C]ornithine. Single tube feedings of varying levels of L-tryptophan (2.5-30 mg/100 g body wt) to overnight-fasted rats 1 hr before sacrifice exhibited increases in the hepatic ODC activities. L-Tryptophan (30 mg/100 g body wt) tube fed to overnight-fasted rats 1/6 to 12 hr before sacrifice induced hepatic ODC activities which were significantly elevated beginning at 1 hr and peaking at 2 hr (6.5-fold increase over controls). In vitro [14C]leucine incorporation into protein using hepatic microsomes of tryptophan-treated rats was significantly increased at 1 hr in comparison with that of controls. The tryptophan-induced stimulation of hepatic ODC activity was not affected by prior adrenalectomy but was abolished by pretreatment with cycloheximide. These studies demonstrate that a single feeding of L-tryptophan can significantly enhance in the rat the activity of ODC, a key enzyme in the biosynthesis of polyamines.
Exp Mol Pathol 1983 Jun
PMID:Tryptophan-induced stimulation of hepatic ornithine decarboxylase activity in the rat. 685 8

All the five enzymes of urea synthesis and the formation of urea in vitro can already be demonstrated in human liver as early as the 9th week of fetal development. At this stage the activity of carbamoyl phosphate synthetase is the highest, whereas that of ornithine carbamoyltransferase is the lowest as compared to those in the adult. The kinetic parameters of the urea cycle enzymes are the same in fetal liver as in adult liver, except that the Km values of ornithine carbamoyltransferase for L-ornithine are 3.5 mM and 0.42 mM in the fetus and in adult liver, respectively. Urea formation in vivo seems to begin in the second half of fetal life, and a gradual increase can be detected in the activity of the enzymes of urea synthesis. The activity of ornithine decarboxylase, the glutamine-dependent carbamoyl phosphate synthetase and aspartate carbamoyltransferase, however, changes in the opposite direction. The concentration of carbamoyl phosphate and aspartate remains constant, but that of ornithine gradually decreases during ontogenesis. The ornithine, carbamoylphosphate and aspartate pools are probably utilized in the polyamine, pyrimidine and urea syntheses at varying rates.
Mol Cell Biochem 1982 Mar 19
PMID:Urea cycle enzymes in human liver: ontogenesis and interaction with the synthesis of pyrimidines and polyamines. 708 58


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>