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At least 631 records · Page 35Linked to original sources
PubMed1997

Arginase in lactating bovine mammary glands: implications in proline synthesis.

The occurrence and subcellular distribution of arginase have been studied in mammary glands from lactating dairy cattle. The enzyme appears to be localized in the mitochondrial fraction, although a significant amount has been found to be associated with the cytosolic fraction. Both mitochondrial and cytosolic arginase are activated by heating with Mn2+. The Michaelis constants for the two fractions, however, are different: 49.5 and 18.5 mM for the mitochondrial fraction and cytosolic fraction, respectively. Overall the total enzyme concentration in the gland suggests that these enzymes contribute to the conversion of arginine to ornithine. Ornithine, in turn, may be converted by ornithine aminotransferase into an intermediate, L-delta 1-pyrroline-5-carboxylate; concurrently. alpha-keto-glutarate is transformed into glutamic acid. Finally, pyrroline-5-carboxylate reductase yields proline, an important amino acid that is needed for casein synthesis. Because pyrroline-5-carboxylate reductase requires NADPH, and because ornithine aminotransferase uses alpha-ketoglutarate, this new pathway is linked to the Krebs cycle through the cytosolic isocitrate dehydrogenase, which is the source of both of these intermediates.

Animals↗
PubMed2003

Nitric oxide-independent CTL suppression during tumor progression: association with arginase-producing (M2) myeloid cells.

Most of the mice bearing a s.c. BW-Sp3 lymphoma tumor mount a CD8(+) T cell-mediated response resulting in tumor regression. Nonetheless, tumor progression occurs in some of the recipients and is associated with CTL inactivity. We demonstrated that T cell-activating APC were induced in regressors whereas T cell suppressive myeloid cells predominated in the spleen of progressors. Indeed, in vitro depletion of either the adherent or the CD11b(+) populations restored T cell cytotoxicity and proliferation in these mice. This CTL inhibition was cell-to-cell contact-dependent but not mediated by NO. However, the same progressor suppressive cells prevented the activity of in vitro-restimulated CTLs derived from regressors in a cell-to-cell contact and NO-dependent fashion. Thus, either the NO-dependent or -independent suppressive pathway prevailed, depending on the target CTL population. In addition, the suppressive population expressed a high arginase activity, suggesting an association of the suppressive phenotype with alternatively activated (M2) myeloid cells. However, the high arginase activity is not directly involved in the suppressive process. Our results provide new insights for myeloid cell-mediated CTL inhibition during cancer progression.

Animals↗
PubMed1999

Arginase and ornithine, as markers in human non-small cell lung carcinoma.

The arginase activity and ornithine level were determined in tissue obtained from patients with non-small cell lung carcinoma (NSLC). The arginase activity and ornithine level in tumor tissues were 1.89 +/- 1.28 U/mg protein and 42.32 +/- 25.82 nmol/mg protein, respectively versus 0.67 +/- 0.19 U/mg protein and 10.12 +/- 3.69 nmol/mg protein for normal tissues (p < 0.01).

Adenocarcinoma↗
PubMed1976

Use of enzyme-loaded erythrocytes in in-vitro correction of arginase-deficient erythrocytes in familial hyperargininemia.

The capacity of arginase-deficient erythrocytes of patients with familial hyperargininemia to produce urea and to catabolize arginine can be increased in vitro by introducing human liver arginase into their erythrocytes. The results of this study on a specific human model show that it is possible to change the metabolic function of a genetically defective erythrocyte by incorporating exogenous human enzyme. The in vivo application of enzyme-loaded erythrocytes for enzyme replacement therapy of inborn metabolic errors in humans must await in vivo studies on animal models.

Amino Acid Metabolism, Inborn Errors↗
PubMed1975

[Amniotic fluid arginase in women at term].

Study on 34 cases. A considerable arginasic activity is observed in amniotic fluid in women at the end of pregnancy. This activity is weak, but increased by Mn2+ (about 5 to 8 times). The total amniotic fluid is more active than the surpernatant, the deposit of which has been eliminated. An important part of arginasic activity results from the elements of the deposit (amniotic cells, foetal cells and eventualy erythrocytes in hemorragic amniotic fluid).

Amniotic Fluid↗
PubMed1992

[The effect of low density lipoprotein (LDL) on NO formation and on arginase activity in mouse peritoneal macrophages].

A large body of the evidence is available to the causative relationship between the elevated blood plasma concentrations of LDL and the atherogenesis. The oxid-LDL (modified LDL) is internalized more rapidly by the macrophages, and there is now substantial evidence that the modified LDL is actually present in atherosclerotic lesions. Recently it has been proved that the endothel cells and monocyta/macrophages generate nitric oxide (NO) from arginine, and that the LDL inhibits the formation of NO in endothel cells. The authors found that the human LDL in vitro exerts an inhibitory effect on the formation of NO in murine PED (peritoneal exudate cells) and synchronously severalfold increasing of the arginase activity in the culture media. Both effects of LDL proved to be dose dependent and the oxid-LDL has been found to be more effective. The increased activity of arginase provides a very likely explanation for the reducing of NO production in macrophage treated by LDL. The reducing or blocking of NO-formation causes a local vasocontraction which induces clinical symptoms.

Animals↗
PubMed1991

An enzymatic route to L-ornithine from L-arginine--activation and stabilization studies on L-arginase.

L-ornithine has growth potential for parenteral nutrition and as a component for biologically active peptides. A process for enzymatic conversion of L-arginine to L-ornithine with arginase has been developed and tested on a pilot scale. With activation of arginase by Mn2+ and stabilization by ascorbic acid, the enzyme is sufficiently active and stable for application in large-scale L-ornithine synthesis.

Arginase↗
PubMed1987

Purification and characterization of arginase from Neurospora crassa.

We have purified an enzymatically active form of arginase from a wild-type strain of Neurospora crassa to homogeneity. The enzyme has a subunit molecular weight of 38,300 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The native protein migrated as a hexamer during gel-filtration chromatography with an apparent molecular weight of 266,000. The enzyme exhibited hyperbolic kinetics at pH 9.5 with an apparent Km for arginine of 131 mM. Antiserum was prepared against the purified enzyme and used to demonstrate the existence of three cross-reactive proteins in crude extracts of wild-type N. crassa. One of these proteins corresponded to the purified protein, whereas the other two were of molecular weights 41,700 and 26,800, respectively. Using the same antiserum, we found that rat liver, but not rat kidney, contains immunoreactive material. We also detected two proteins in extracts of Saccharomyces cerevisiae that were weakly cross-reactive with the antiserum. These data provide evidence for the existence of multiple forms of arginase in fungi as well as in mammals.

Animals↗
PubMed1986

The quaternary structure of ornithine transcarbamoylase and arginase from Saccharomyces cerevisiae.

Electron microscopic studies employing negative staining, rotary shadowing, and unidirectional shadowing have revealed the subunit architecture of ornithine transcarbamoylase and arginase from Saccharomyces cerevisiae. These techniques have confirmed the quaternary structure of these enzymes, and have permitted an estimate of the shape and dimensions of each of the individual enzymes as well as those of the corresponding subunits to be determined. Both enzymes are trimers exhibiting 3-fold rotational symmetry with subunits which are oblate ellipsoids of revolution. The overall dimensions determined for ornithine transcarbamoylase are a height of 39 A and a width of 102 A. The consequent subunit dimensions are 59 X 59 X 39 A, yielding a subunit axial ratio of 1.51. Arginase has a height of 42 A and a width of 97 A. The subunit dimensions are 56 X 56 X 42 A, yielding a subunit axial ratio of 1.33. The hydrodynamic behavior of the two enzymes is fully consistent with this molecular architecture, suggesting that the structures proposed here are similar to those of the proteins in aqueous solution.

Arginase↗
PubMed1985

[Effect of arginine on the arginase activity and urea content of the brain and liver of rats acclimating to cold].

At cold stress (3 days exposition at 2--4 degrees C) the urea formation in rats brain and liver does not become more active, the content of extraerythrocytic hemoglobin and the total peroxydase activity increase in blood serum, the animals sensitivity to the action of hyperbaric oxygenation (HB0) grows. At cold adaptation (45 days at 2--4 degrees C) the urea content in tissues and the activity of arginase in liver increase, the concentration of extraerythrocytic hemoglobin and the total peroxydase activity normalize, animals become more resistant to HB0. Every day administration of arginine during 3-day cold effect makes the brain and liver arginase on 42 and 28% more active, increases the urea content on 26 and 19%, stabilizes the erythrocytic membranes. The animals protected by arginine against cold are more resistant to the action of HB0.

Acclimatization↗
PubMedDate not supplied

[Brain arginase isoenzyme activity during the growth of neurinomas].

Activity of arginase and of its isoenzymes was studied in rat brain tissue and in neurinoma tissue (strain 10-13-3) at the period of growth of the tumor in trigeminal nerve. Within the fourth day after the tumor transplantation the total activity of arginase was increased in brain and distinct alterations were found in the isoenzyme spectrum, mainly in the impaired hemisphere. The enzymatic activity was increased in the tumoral tissue within 16 days; the activation was localized in the malignant tissue and did not extent into surrounding nerves. In all the samples studied the positively charged isoenzyme I was activated, whereas the activity of the isoenzyme II was altered only slightly and usually tended to decrease. It was the activity of the isoenzyme I, which appeared to be altered in the growing tumor.

Animals↗
PubMed1979

[Importance of arginine content and arginase activity in fertility].

Experimental studies have shown that in men with pathospermia the arginine content of sperm plasma is lower than in normal men. In order to find out the reason of this divergency the authors analysed the content of arginine, urea, citrulline, GAA and arginase activity in serum and in sperm plasma of 40 patients with normo-, oligo- or azoospermia. For the first time our results show that the low arginine content in pathological sperm is not due to disorder of the precursor metabolism, but to the increased arginase activity and to the increased conversion of arginine to GAA. In order to find out the mechanism of action and to develop an adequate andrological therapy detailed studies on molecular level have to be done.

Arginase↗
PubMed1978

[Arginase activity in the liver of growing rats with manganese deficiency].

Rats weaned early at 13 days of age exhibited at 10% lower growth within 6 weeks when Mn supply was deficient compared to control animals (P is less than 0.005). While the reduction of the dietary Mn content from 50 to 6 ppm did not yet affect growth, the animals already showed a 60% lower arginase activity at this median level of Mn supply. The values of the depleted animals (0.7 ppm Mn) had fallen by 71% compared to the control group. Therefore, the arginase values may be applied to differentiate between suboptimum and optimum Mn supply.

Animals↗
PubMed1978

[Control of argininosuccinate synthetase, argininosuccinase and arginase activities in the newborn rat].

Some factors influencing the postnatal development of three urea cycle enzyme activities, argininosuccinate synthetase, argininosuccinase, and arginase, in the liver of newborn rats, are studied. Premature and postmature birth change the developmental pattern of these enzyme activities, suggesting that the increase in enzyme activity after birth is initiated by the birth process. Starvation of newborn animals after birth has no effect on the postnatal development of the three enzyme activities. Bilateral adrenalectomy at birth causes a partial inhibition of the postnatal increase of argininosuccinase and arginase activities while injection of cortisol prevents the effects of adrenalectomy. It is suggested that presence of adrenal secretion is one condition necessary for the increased activity of the prematures.

Adrenalectomy↗
PubMed1982

Regulation of glucocorticoids of arginase and argininosuccinate synthetase in cultured rat hepatoma cells.

We have examined and characterized the regulation by glucocorticoids of the levels of arginase and argininosuccinate synthetase in two rat hepatoma cell lines (H4-II-E-C3 and MH1C1). Hydrocortisone elevates the activity of both enzymes in a time- and dose-dependent fashion. This effect was blunted markedly by small amounts of ethanol (0.1 to 0.9% [v/v]) and blocked substantially by a high molar excess of the "anti-inducer" steroid fluoxymesterone. The other "optimal" inducers dexamethasone and corticosterone were as effective as hydrocortisone in elevating the levels of these enzymes at saturating concentrations. Inhibition of these stimulations by cycloheximide indicated that ongoing cellular protein synthesis was required for both effects, and the admixture of extracts from fully stimulated and basal cells gave no evidence for the existence of direct inhibitors or activators of either enzyme. The results corroborate findings from earlier whole-animal studies and provide evidence for the following conclusions. (i) This stimulation by hydrocortisone of urea-cycle enzymes in the cultured hepatoma cells is mediated by a classical glucocorticoid mechanism involving initial binding to specific cytoplasmic steroid receptors and the eventual accumulation of new enzyme molecules. (ii) These cell lines thus constitute valid experimental models for use in further detailed studies on the molecular mechanism(s) through which glucocorticoids and intermediary metabolites effect a selective modulation of arginase and argininosuccinate-synthetase gene expression in the differentiated mammalian liver.

Animals↗
PubMedDate not supplied

[Temperature dependence of the arginase activity of the plerocercoids of Triaenophorus nodulosus and Diphyllobothrium latum].

The effect of temperature on the arginase enzyme activity in Triaenophorus nodulosus and Diphyllobothrium latum was studied. The temperature optimum of arginase of T. nodulosus (definitive hosts are fishes) is at 27 degrees while in D. latum it is at 57 degrees. It has been inferred that a certain preadaptation of some enzyme properties (temperature optimum, thermostabolity) to a temperature regime of a definitive host takes place. Biochemical mechanisms of preadaptation of enzyme systems of helminths to temperature are discussed.

Adaptation, Physiological↗
PubMed1981

[Physico-chemical properties of guinea pig liver arginase (author's transl)].

Arginase (E.C. 3.5.3.1) the enzyme which catalyses the hydrolysis of arginine to ornithine and urea has been investigated in guinea pig liver in relation to the kinetic constants of its substrate and inhibitors as well as to other physico-chemical properties. The results show that the enzyme has Km value of 19.6 mM for its substrate L-arginine and is competitively inhibited by one of its reaction products, the L-ornithine, and also by L-lysine and diaminopymelic acid. Optimal activity of the enzyme occurs at 10.5 pH and maximal stability in the range of 6.5 to 7.5 pH. The mentioned arginase exhibits temperature dependent activity and stability, being 64 degrees C (15 min and pH 7.5) the half-inactivation temperature. An increase in the activity and temperature stability of the enzyme, when previously activated by heating for 5 min at 45 degrees C in the presence of 10 mM MnCl2, has been achieved.

Animals↗