1
|
Fitzpatrick JM, Fuentes JM, Chalmers IW, Wynn TA, Modolell M, Hoffmann KF, Hesse M. Schistosoma mansoni arginase shares functional similarities with human orthologs but depends upon disulphide bridges for enzymatic activity. Int J Parasitol 2009; 39:267-79. [PMID: 18723022 PMCID: PMC2756234 DOI: 10.1016/j.ijpara.2008.06.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2008] [Revised: 06/11/2008] [Accepted: 06/13/2008] [Indexed: 11/19/2022]
Abstract
Schistosome helminths constitute a major health risk for the human population in many tropical areas. We demonstrate for the first time that several developmental stages of the human parasite Schistosoma mansoni express arginase, which is responsible for the hydrolysis of l-arginine to l-ornithine and urea. Arginase activity by alternatively activated macrophages is an essential component of the mammalian host response in schistosomiasis. However, it has not been previously shown that the parasite also expresses arginase when it is in contact with the mammalian host. After cloning and sequencing the cDNA encoding the parasite enzyme, we found that many structural features of human arginase are well conserved in the parasite ortholog. Subsequently, we discovered that S. mansoni arginase shares many similar molecular, biochemical and functional properties with both human arginase isoforms. Nevertheless, our data also reveal striking differences between human and schistosome arginase. Particularly, we found evidence that schistosome arginase activity depends upon disulphide bonds by cysteines, in contrast to human arginase. In conclusion, we report that S. mansoni arginase is well adapted to the physiological conditions that exist in the human host.
Collapse
|
2
|
Mavri-Damelin D, Damelin LH, Eaton S, Rees M, Selden C, Hodgson HJF. Cells for bioartificial liver devices: the human hepatoma-derived cell line C3A produces urea but does not detoxify ammonia. Biotechnol Bioeng 2008; 99:644-51. [PMID: 17680661 DOI: 10.1002/bit.21599] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Extrahepatic bioartificial liver devices should provide an intact urea cycle to detoxify ammonia. The C3A cell line, a subclone of the hepatoma-derived HepG2 cell line, is currently used in this context as it produces urea, and this has been assumed to be reflective of ammonia detoxification via a functional urea cycle. However, based on our previous findings of perturbed urea-cycle function in the non-urea producing HepG2 cell line, we hypothesized that the urea produced by C3A cells was via a urea cycle-independent mechanism, namely, due to arginase II activity, and therefore would not detoxify ammonia. Urea was quantified using (15)N-ammonium chloride metabolic labelling with gas chromatography-mass spectrometry. Gene expression was determined by real-time reverse transcriptase-PCR, protein expression by western blotting, and functional activities with radiolabelling enzyme assays. Arginase inhibition studies used N(omega)-hydroxy-nor-L-arginine. Urea was detected in C3A conditioned medium; however, (15)N-ammonium chloride-labelling indicated that (15)N-ammonia was not incorporated into (15)N-labelled urea. Further, gene expression of two urea cycle genes, ornithine transcarbamylase and arginase I, were completely absent. In contrast, arginase II mRNA and protein was expressed at high levels in C3A cells and was inhibited by N(omega)-hydroxy-nor-L-arginine, which prevented urea production, thereby indicating a urea cycle-independent pathway. The urea cycle is non-functional in C3A cells, and their urea production is solely due to the presence of arginase II, which therefore cannot provide ammonia detoxification in a bioartificial liver system. This emphasizes the continued requirement for developing a component capable of a full repertoire of liver function.
Collapse
Affiliation(s)
- Demetra Mavri-Damelin
- Centre for Hepatology at the Royal Free-Hampstead Campus, Royal Free and University College Medical School, London NW3 2PF, UK.
| | | | | | | | | | | |
Collapse
|
3
|
Kropf P, Baud D, Marshall SE, Munder M, Mosley A, Fuentes JM, Bangham CRM, Taylor GP, Herath S, Choi BS, Soler G, Teoh T, Modolell M, Müller I. Arginase activity mediates reversible T cell hyporesponsiveness in human pregnancy. Eur J Immunol 2007; 37:935-45. [PMID: 17330821 PMCID: PMC2699382 DOI: 10.1002/eji.200636542] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2006] [Revised: 11/15/2006] [Accepted: 02/01/2007] [Indexed: 11/24/2022]
Abstract
Complex regulation of T cell functions during pregnancy is required to ensure materno-fetal tolerance. Here we reveal a novel pathway for the temporary suppression of maternal T cell responses in uncomplicated human pregnancies. Our results show that arginase activity is significantly increased in the peripheral blood of pregnant women and remarkably high arginase activities are expressed in term placentae. High enzymatic activity results in high turnover of its substrate L-arginine and concomitant reduction of this amino acid in the microenvironment. Amino acid deprivation is emerging as a regulatory pathway of lymphocyte responses and we assessed the consequences of this enhanced arginase activity on T cell responses. Arginase-mediated L-arginine depletion induces down-regulation of CD3 zeta, the main signalling chain of the TCR, and functional T cell hyporesponsiveness. Importantly, this arginase-mediated T cell suppression was reversible, as inhibition of arginase activity or addition of exogenous L-arginine restored CD3 zeta chain expression and T cell proliferation. Thus, L-arginine metabolism constitutes a novel physiological mechanism contributing to the temporary suppression of the maternal immune response during human pregnancy.
Collapse
Affiliation(s)
- Pascale Kropf
- Department of Immunology, Faculty of Medicine, Imperial College LondonLondon, UK
| | - David Baud
- Department of Obstetrics and Gynaecology, St. Mary's HospitalLondon, UK
| | - Sara E Marshall
- Department of Immunology, Faculty of Medicine, Imperial College LondonLondon, UK
| | - Markus Munder
- Department of Hematology, Oncology, and Rheumatology, University Hospital HeidelbergHeidelberg, Germany
| | - Angelina Mosley
- Department of Immunology, Faculty of Medicine, Imperial College LondonLondon, UK
| | - José M Fuentes
- Departamento de Bioquímica y Biología Molecular, E.U. Enfermería y T.O., Universidad de ExtremaduraCáceres, Spain
| | - Charles R M Bangham
- Department of Immunology, Faculty of Medicine, Imperial College LondonLondon, UK
| | - Graham P Taylor
- Department of Genito-Urinary Medicine and Communicable Diseases, Imperial CollegeLondon, UK
| | - Shanti Herath
- Department of Veterinary Clinical Sciences, Royal Veterinary CollegeLondon, UK
| | - Beak-San Choi
- Department of Immunology, Faculty of Medicine, Imperial College LondonLondon, UK
| | - Germán Soler
- Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad de ExtremaduraCáceres, Spain
| | - Tg Teoh
- Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad de ExtremaduraCáceres, Spain
| | - Manuel Modolell
- Department of Cellular Immunology, Max-Planck-Institute for ImmunobiologyFreiburg, Germany
| | - Ingrid Müller
- Department of Immunology, Faculty of Medicine, Imperial College LondonLondon, UK
| |
Collapse
|
4
|
Mavri-Damelin D, Eaton S, Damelin LH, Rees M, Hodgson HJF, Selden C. Ornithine transcarbamylase and arginase I deficiency are responsible for diminished urea cycle function in the human hepatoblastoma cell line HepG2. Int J Biochem Cell Biol 2006; 39:555-64. [PMID: 17098461 DOI: 10.1016/j.biocel.2006.10.007] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2006] [Revised: 10/02/2006] [Accepted: 10/11/2006] [Indexed: 11/29/2022]
Abstract
A possible cell source for a bio-artificial liver is the human hepatblastoma-derived cell line HepG2 as it confers many hepatocyte functions, however, the urea cycle is not maintained resulting in the lack of ammonia detoxification via this cycle. We investigated urea cycle activity in HepG2 cells at both a molecular and biochemical level to determine the causes for the lack of urea cycle expression, and subsequently addressed reinstatement of the cycle by gene transfer. Metabolic labelling studies showed that urea production from 15N-ammonium chloride was not detectable in HepG2 conditioned medium, nor could 14C-labelled urea cycle intermediates be detected. Gene expression data from HepG2 cells revealed that although expression of three urea cycle genes Carbamoyl Phosphate Synthase I, Arginosuccinate Synthetase and Arginosuccinate Lyase was evident, Ornithine Transcarbamylase and Arginase I expression were completely absent. These results were confirmed by Western blot for arginase I, where no protein was detected. Radiolabelled enzyme assays showed that Ornithine Transcarbamylase functional activity was missing but that Carbamoyl Phosphate Synthase I, Arginosuccinate Synthetase and Arginosuccinate Lyase were functionally expressed at levels comparable to cultured primary human hepatocytes. To restore the urea cycle, HepG2 cells were transfected with full length Ornithine Transcarbamylase and Arginase I cDNA constructs under a CMV promoter. Co-transfected HepG2 cells displayed complete urea cycle activity, producing both labelled urea and urea cycle intermediates. This strategy could provide a cell source capable of urea synthesis, and hence ammonia detoxificatory function, which would be useful in a bio-artificial liver.
Collapse
Affiliation(s)
- Demetra Mavri-Damelin
- The UCL Institute of Hepatology, Hampstead Campus, Royal Free and University College Medical School, Rowland Hill Street, London NW3 2PF, UK.
| | | | | | | | | | | |
Collapse
|
5
|
Kropf P, Fuentes JM, Fähnrich E, Arpa L, Herath S, Weber V, Soler G, Celada A, Modolell M, Müller I. Arginase and polyamine synthesis are key factors in the regulation of experimental leishmaniasis in vivo. FASEB J 2005; 19:1000-2. [PMID: 15811879 DOI: 10.1096/fj.04-3416fje] [Citation(s) in RCA: 221] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Arginase 1, an enzyme induced by Th2 cytokines, is a hallmark of alternatively activated macrophages and is responsible for the hydrolysis of L-arginine into ornithine, the building block for the production of polyamines. Upregulation of arginase 1 has been observed in a variety of diseases, but the mechanisms by which arginase contributes to pathology are not well understood. We reveal here a unique role for arginase 1 in the pathogenesis of nonhealing leishmaniasis, a prototype Th2 disease, and demonstrate that the activity of this enzyme promotes pathology and uncontrolled growth of Leishmania parasites in vivo. Inhibition of arginase activity during the course of infection has a clear therapeutic effect, as evidenced by markedly reduced pathology and efficient control of parasite replication. Despite the clear amelioration of the disease, this treatment does not alter the Th2 response. To address the underlying mechanisms, the arginase-induced L-arginine catabolism was investigated and the results demonstrate that arginase regulates parasite growth directly by affecting the polyamine synthesis in macrophages.
Collapse
Affiliation(s)
- Pascale Kropf
- Department of Immunology, Faculty of Medicine, Imperial College London, UK
| | | | | | | | | | | | | | | | | | | |
Collapse
|
6
|
Dzik JM, Gołos B, Jagielska E, Zielinski Z, Wałajtys-Rode E. A non-classical type of alveolar macrophage response to Trichinella spiralis infection. Parasite Immunol 2004; 26:197-205. [PMID: 15367297 DOI: 10.1111/j.0141-9838.2004.00700.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Studies of arginase expression and activity in guinea pig alveolar macrophages during Trichinella spiralis infection, prompted by earlier observation of innate lung response to the parasite, showed the macrophages to express both activity and protein of arginase type I. In cultured macrophages part of the enzyme was found to be always released to the extracellular medium. Whereas BCG in vivo treatment, alone or preceded by T. spiralis infection, stimulated arginase activity, T. spiralis infection alone affected the enzyme distribution between intracellular and extracellular fractions, and properties (K(m) and V(max)), rather than total (intracellular + extracellular) activity, with TGF-beta apparently responsible for a part of the effect. Anti-TGF-beta antibody treatment of the animals influenced both arginase activation by Mn(2+) and dependence of the enzyme-catalysed reaction on pH. Whereas T. spiralis infection activated guinea pig alveolar macrophages by the type II macrophage activation, as indicated by constant arginase expression, associated with previously demonstrated lack of stimulation of nitric oxide production, BCG treatment invoked an alternative type of activation mechanism, reflected by stimulation of macrophage arginase, but not iNOS, activity.
Collapse
Affiliation(s)
- J M Dzik
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warszawa, Poland.
| | | | | | | | | |
Collapse
|
7
|
Müllner N, Lázár A, Hrabák A. Enhanced utilization and altered metabolism of arginine in inflammatory macrophages caused by raised nitric oxide synthesis. Int J Biochem Cell Biol 2002; 34:1080-90. [PMID: 12009303 DOI: 10.1016/s1357-2725(02)00028-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Nitric oxide (NO) production was increased in macrophages during inflammation. Casein-elicitation of rodents causing a peritoneal inflammation offered a good model to study alterations in the metabolism of L-arginine, the precursor of NO synthesis. The utilization of L-arginine for NO production, arginase pathway and protein synthesis were studied by radioactive labeling and chromatographic separation. The expression of NO synthase and arginase was studied by Western blotting.Rat macrophages utilized more arginine than mouse macrophages (228+/-27 versus 71+/-12.8pmol per 10(6) macrophages). Arginine incorporation into proteins was low in both species (<15% of labeling). When NO synthesis was blocked, arginine was utilized at a lower general rate, but L-ornithine formation did not increase. The expression of enzymes utilizing arginine increased. NO production was raised mainly in rats (1162+/-84pmol citrulline per 10(6) cells) while in mice both arginase and NO synthase were active in elicited macrophages (677+/-85pmol ornithine and 456+/-48pmol citrulline per 10(6) cells). We concluded, that inflammation induced enhanced L-arginine utilization in rodent macrophages. The expressions and the activities of arginase and NO synthase as well as NO formation were increased in elicited macrophages. Specific blocking of NO synthesis did not result in the enhanced effectivity of the arginase pathway, rather was manifested in a general lower rate of arginine utilization. Different rodent species reacted differently to inflammation: in rats, high NO increase was found exclusively, while in mice the activation of the arginase pathway was also important.
Collapse
Affiliation(s)
- Nándor Müllner
- Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, VIII. Puskin u. 9., P.O. Box 260, Budapest H-1444, Hungary
| | | | | |
Collapse
|
8
|
Hesse M, Modolell M, La Flamme AC, Schito M, Fuentes JM, Cheever AW, Pearce EJ, Wynn TA. Differential regulation of nitric oxide synthase-2 and arginase-1 by type 1/type 2 cytokines in vivo: granulomatous pathology is shaped by the pattern of L-arginine metabolism. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2001; 167:6533-44. [PMID: 11714822 DOI: 10.4049/jimmunol.167.11.6533] [Citation(s) in RCA: 526] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Type 2 cytokines regulate fibrotic liver pathology in mice infected with Schistosoma mansoni. Switching the immune response to a type 1-dominant reaction has proven highly effective at reducing the pathologic response. Activation of NOS-2 is critical, because type 1-deviated/NO synthase 2 (NOS-2)-deficient mice completely fail to control their response. Here, we demonstrate the differential regulation of NOS-2 and arginase type 1 (Arg-1) by type 1/type 2 cytokines in vivo and for the first time show a critical role for arginase in the pathogenesis of schistosomiasis. Using cytokine-deficient mice and two granuloma models, we show that induction of Arg-1 is type 2 cytokine dependent. Schistosome eggs induce Arg-1, while Mycobacterium avium-infected mice develop a dominant NOS-2 response. IFN-gamma suppresses Arg-1 activity, because type 1 polarized IL-4/IL-10-deficient, IL-4/IL-13-deficient, and egg/IL-12-sensitized animals fail to up-regulate Arg-1 following egg exposure. Notably, granuloma size decreases in these type-1-deviated/Arg-1-unresponsive mice, suggesting an important regulatory role for Arg-1 in schistosome egg-induced pathology. To test this hypothesis, we administered difluoromethylornithine to block ornithine-aminodecarboxylase, which uses the product of arginine metabolism, L-ornithine, to generate polyamines. Strikingly, granuloma size and hepatic fibrosis increased in the ornithine-aminodecarboxylase-inhibited mice. Furthermore, we show that type 2 cytokine-stimulated macrophages produce proline under strict arginase control. Together, these data reveal an important regulatory role for the arginase biosynthetic pathway in the regulation of inflammation and demonstrate that differential activation of Arg-1/NOS-2 is a critical determinant in the pathogenesis of granuloma formation.
Collapse
Affiliation(s)
- M Hesse
- Schistosomiasis Immunology and Pathology Unit and Max Planck Institut für Immunbiologie, Freiburg, Germany
| | | | | | | | | | | | | | | |
Collapse
|
9
|
Mora A, del Ara Rangel M, Fuentes JM, Soler G, Centeno F. Implications of the S-shaped domain in the quaternary structure of human arginase. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1476:181-90. [PMID: 10669784 DOI: 10.1016/s0167-4838(99)00256-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Arginase I is a homotrimeric protein with a binuclear manganese cluster. At the C-terminus of each monomer, the polypeptide chain forms an unusual S-shaped oligomerization motif where the majority of intermonomer contacts are located [Z.F. Kanyo, L.R. Scolnick, D.E. Ash, D.W. Christianson, Nature 383 (1996) 554-557]. In order to study the implication of this motif in the quaternary structure of human arginase I, we have constructed a truncated arginase lacking the 14 C-terminal amino acids, leaving Arg-308 as the last residue in the sequence. The resulting protein retains its trimeric structure, as determined by gel filtration (molecular mass 94 kDa). The same result was obtained in the presence of high ionic strength (KCl 0.5 M). Both data indicate that neither the S-shaped motif nor Arg-308 are fundamental in keeping the trimeric quaternary structure. Data obtained from intrinsic anisotropy and fluorescence intensity studies allow us to predict that the distance between the two unique tryptophans in the sequence is 2.9 nm in the native arginase and 4.1 nm for the truncated mutant. These distances allow us to assume a different conformational state in the truncated arginase without any change in its quaternary structure, suggesting that the carboxy-terminal motif is not the most prominent domain implicated in the quaternary structure of human arginase. Collisional quenching studies reinforce this possibility, since using I(-) as quenching molecule we were able to distinguish the two tryptophans in the truncated arginase. Moreover, kinetic studies show that the truncated mutant was fully active. In summary, the main conclusion about the structure of the human arginase I, derived from our study, is that the C-terminal S-shaped motif is not basic to the maintenance of the quaternary structure nor to the activity of the protein.
Collapse
Affiliation(s)
- A Mora
- Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad de Extremadura, Av. Universidad s/n, 10071, Cáceres, Spain
| | | | | | | | | |
Collapse
|
10
|
Munder M, Eichmann K, Morán JM, Centeno F, Soler G, Modolell M. Th1/Th2-Regulated Expression of Arginase Isoforms in Murine Macrophages and Dendritic Cells. THE JOURNAL OF IMMUNOLOGY 1999. [DOI: 10.4049/jimmunol.163.7.3771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Abstract
Activated murine macrophages metabolize arginine by two alternative pathways involving the enzymes inducible NO synthase (iNOS) or arginase. The balance between the two enzymes is competitively regulated by Th1 and Th2 T helper cells via their secreted cytokines: Th1 cells induce iNOS, whereas Th2 cells induce arginase. Whereas the role of macrophages expressing iNOS as inflammatory cells is well established, the functional competence of macrophages expressing arginase remains a matter of speculation. Two isoforms of mammalian arginases exist, hepatic arginase I and extrahepatic arginase II. We investigated the regulation of arginase isoforms in murine bone marrow-derived macrophages (BMMΦ) in the context of Th1 and Th2 stimulation. Surprisingly, in the presence of either Th2 cytokines or Th2 cells, we observe a specific induction of the hepatic isoform arginase I in BMMΦ. Induction of arginase I was shown on the mRNA and protein levels and obeyed the recently demonstrated synergism among the Th2 cytokines IL-4 and IL-10. Arginase II was detectable in unstimulated BMMΦ and was not significantly modulated by Th1 or Th2 stimulation. Similar to murine BMMΦ, murine bone marrow-derived dendritic cells, as well as a dendritic cell line, up-regulated arginase I expression and arginase activity upon Th2 stimulation, whereas arginase II was never detected. In addition to revealing the unexpected expression of arginase I in the macrophage/monocyte lineage, these results uncover a further intriguing parallelism between iNOS and arginase: both have a constitutive and an inducible isoform, the latter regulated by the Th1/Th2 balance.
Collapse
Affiliation(s)
- Markus Munder
- *Max-Planck-Institut für Immunbiologie, Freiburg, Germany; and
| | - Klaus Eichmann
- *Max-Planck-Institut für Immunbiologie, Freiburg, Germany; and
| | - José M. Morán
- †Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad de Extremadura, Cáceres, Spain
| | - Francisco Centeno
- †Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad de Extremadura, Cáceres, Spain
| | - Germán Soler
- †Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad de Extremadura, Cáceres, Spain
| | - Manuel Modolell
- *Max-Planck-Institut für Immunbiologie, Freiburg, Germany; and
| |
Collapse
|
11
|
Abstract
Arginase is a primordial enzyme, widely distributed in the biosphere and represented in all primary kingdoms. It plays a critical role in the hepatic metabolism of most higher organisms as a cardinal component of the urea cycle. Additionally, it occurs in numerous organisms and tissues where there is no functioning urea cycle. Many extrahepatic tissues have been shown to contain a second form of arginase, closely related to the hepatic enzyme but encoded by a distinct gene or genes and involved in a host of physiological roles. A variety of functions has been proposed for the "extrahepatic" arginases over the last three decades. In recent years, interest in arginase has been stimulated by a demonstrated involvement in the metabolism of the ubiquitous and multifaceted molecule nitric oxide. Molecular biology has begun to furnish new clues to the disparate functions of arginases in different environments and organisms. Comparative studies of arginase sequences are also beginning to elucidate the comparative evolution of arginases, their molecular structures and the nature of their catalytic mechanism. Further studies have sought to clarify the involvement of arginase in human disease. This review presents an outline of the current state of arginase research by giving a comparative overview of arginases and their associated properties.
Collapse
Affiliation(s)
- C P Jenkinson
- Mental Retardation Research Center, University of California, Los Angeles 90024-1759, USA.
| | | | | |
Collapse
|