Microheterogeneity of molecular forms of arginase in mammalian tissues

Two isoforms of arginase, A1 and A2, were found in rat liver, submaxillary gland and kidney as well as beef kidney. In beef liver, however, A2 was the only detectable form. Two additional forms, A3 and A4, found only in rat kidney were probably artifactitious. A1 and A2 exhibited chromatographic and immunological microheterogeneity. While A1 in rat liver and submaxillary gland was excluded by DEAE-cellulose (pH 8.3) and retained on CM-cellulose (pH 7.5), that (A'1) in beef and rat kidneys was excluded by both ion-exchangers. A2 in all tissues was retained on DEAE-cellulose, but not on CM-cellulose. Both A1 and A2 in rat liver and beef kidney, A1 from rat submaxillary gland and A2 from beef liver were precipitated by antibodies to rat and beef liver arginases. None of the forms in rat kidney (A1, A2, A3 and A4) showed any cross-reactivity to either antibody. Rat submaxillary gland A2 was precipitated by anti-rat liver arginase, but activated by anti-beef liver arginase. While the major molecular forms were A1 in rat liver and submaxillary gland and A2 in beef liver and rat kidney, the two forms occurred in equal proportions in beef kidney. It appears that different isoforms might function as components of the urea cycle in the liver of different mammals and of the arginine catabolic pathway in different extrahepatic tissues.     

Purification and properties of liver arginase from teleostean fish Clarias batrachus (L.).

Liver arginase of Clarias batrachus has been purified to 56.3-fold employing ammonium sulphate fraction, DEAE-cellulose and CM-cellulose chromatography. Bidirectional polyacrylamide gel electrophoresis shows the presence of two isoenzymes of arginase. The enzyme has a molecular weight of about 87,000 and Km 15.38 mM for L-arginine, optimum pH 9.5 and temperature 37 degrees C. Ornithine and leucine as competitive whereas valine and isoleucine act as non-competitive inhibitors with respect to L-arginine as substrate.     

Types of arginase in rat tissues.

Significant amounts of arginase activity were found in homogenates of submaxillary salivary gland and epididymis, as well as of liver, kidney, mammary gland, and small intestine. The isoelectric point of arginase solubilized from kidney was at pH 7.0 in contrast to that of pH 9.4 characteristic of hepatic arginase in rat. The isozymic variants of arginase in the different tissues were identified by their electrophoretic migration on polyacrylamide gels and by titration of the enzymes against antibody prepared against purified rat liver arginase. Antibody titrations confirmed the indications obtained by electrophoresis that one type of arginase is limited to hepatic tissues (and possibly submaxillary gland) while the other type is found in all other tissues. The physiological role of arginase in hepatic tissues has been previously associated with the urea cycle; the possible function of arginase in proline synthesis in other tissues remains to substantiated.     

The isolation and immunological properties of two arginase forms from human erythrocytes

1. Two forms of arginase were isolated from human erythrocytes; the main form adsorbed on CM-cellulose and the second form, occurring in much smaller amount, adsorbed on DEAE-cellulose. 2. The molecular weight of either arginase was 120,000 +/- 5000. 3. The erythrocyte arginases are similar in immunological properties to arginase A4 from human kidney and A2 from human liver, respectively. 4. Despite the literature data stating that human erythrocyte arginase and human liver arginase are identical, it was found that the main forms of arginase of these tissues A4 from erythrocytes and A5 from liver differ in immunological properties.     

Substrate inhibition of rat liver and kidney arginase with fluoride

Fluoride is an uncompetitive inhibitor of rat liver arginase. This study has shown that fluoride caused substrate inhibition of rat liver arginase at substrate concentrations above 4 mM. Rat kidney arginase was more sensitive to inhibition by fluoride than liver arginase. For both liver and kidney arginase preincubation with fluoride had no effect on the inhibition. When assayed with various concentrations of L-arginine, rat kidney arginase did not have Michaelis-Menten kinetics. Lineweaver-Burk and Eadie-Hofstee plots were nonlinear. Kidney arginase showed strong substrate activation at concentrations of L-arginine above 4 mM. Within narrow concentrations of L-arginine, the inhibition of kidney arginase by fluoride was uncompetitive. Fluoride caused substrate inhibition of kidney arginase at L-arginine concentrations above 1 mM. The presence of fluoride prevented the substrate activation of rat kidney arginase.     

Isoenzyme pattern and immunological properties of arginase in normal and hyperargininemia fibroblasts

Arginase deficiency is an inborn error of the last step in the urea cycle and leads to profound hyperargininemia. The enzyme deficiency has been demonstrated in the liver and red blood cells. In cultured patient fibroblasts, the activity is normal. Arginase exists in multiple molecular forms only one of which is missing in hyperargininemic patients. In fibroblasts, three arginase isoenzymes can be demonstrated by DEAE-cellulose column chromatography, two by electrophoresis and by immunoprecipitation methods. From the present data, it is improbable that part of the A1 isoenzyme in fibroblasts originates from fetal calf serum arginase which supplements the culture media. None of the techniques for the separation and analyses of arginase isoenzyme allows to differentiate between the normal and the arginase-deficient phenotype. A possible explanation would be that the defect in A1 arginase observed in the liver is the result of a regulatory defect.     

Production and characterization of monoclonal antibodies to rat liver arginase

Rat liver arginase was purified and five monoclonal antibodies were produced by fusion of spleen cells from a Balb/c mouse and the myeloma cell line P3-X36-Ag-U1. One, R2D19, of five antibodies belonged to the IgG2a subclass, the other four, R1D81, R1G11, R2E10, and R2G51, were of the IgG1 type. The R1D81 cross-reacted with human liver arginase. This antibody inhibited the arginase activity, competing with arginine. These results suggest that R1D81 binds to the catalytic site of arginase. The R2D19 also inhibited the enzyme activity but acted as a noncompetitive inhibitor. With the use of R1D81 and a polyclonal anti-human liver arginase antibody conjugated with alkaline phosphatase, a sandwich enzyme-linked immunosorbent assay (ELISA) was developed for the quantification of human arginase. Specificity of monoclonal antibodies for rat liver arginase was examined by means of the sandwich ELISA. Eight pairs of monoclonal antibodies could form a sandwich with the arginase. Only the R2E10 could be used for both the first and the second antibody in the sandwich system. In other cases, monoclonal antibodies could not be interchanged between solid and liquid phase.     

Reactivation of the EDTA-treated arginase from rat and calf liver.

1. The anionic calf liver arginase, like the cationic rat liver enzyme, is inactivated by EDTA-treatment. The activity is fully restored by Mn2+. A smaller effect is observed with Cd2+, Ni2+ and Co2+. 2. The EDTA-inactivated calf liver arginase, unlike the rat liver enzyme, does not dissociate into subunits, and its mol.wt. (120 000) is unchanged. 3. The reactivation of rat liver arginase subunits (mol.wt. 30 000) by Ni2+ is accompanied, similarly as in the case of Mn2+, by reassociation to the form of mol.wt. 120 000, i.e. the same as for the native enzyme. 4. It is suggested that Mn2+ in arginase is bound at the active site and at the site responsible for maintenance of the oligomeric structure. In calf liver enzyme this binding site is inaccessible to the chelating agent.     

Inhibition of rat liver and kidney arginase by cadmium ion

Cadmium ion activates arginase from many species of organisms but is an inhibitor of arginase from many other species. The purpose of this study was to investigate the inhibition of rat liver and kidney arginase by cadmium ion. Rat kidney arginase was inhibited by much lower concentrations of cadmium ion than rat liver arginase. Cadmium ion was a mixed noncompetitive inhibitor of both rat liver and kidney arginase. Cadmium ion enhanced the substrate activation of rat kidney arginase while still inhibiting the enzyme. Cadmium ion prevented the substrate inhibition of rat kidney arginase by fluoride while still inhibiting the enzyme. Cadmium ion also inhibited rat kidney arginase in the presence of manganese ion.     

A comparative polyacrylamide gel electrophoretic study of arginase in vertebrate tissues

The electrophoretic behaviour of arginase in the tissue extracts of rat, beef, lizard and frog was studied by bidirectional polyacrylamide gel electrophoresis. The enzyme from rat liver and submaxillary gland migrated to the cathode with the activity concentrated in a single peak. Arginase from beef liver emerged as a single peak of anodal migration with a significant shoulder in the sample gel. Frog liver and kidney enzymes also appeared as single peaks with a distinct anodal movement. The activity in mammalian kidney and lizard liver and kidney resolved into two peaks of anodal migration suggesting the presence of two isoenzymes of arginase in these tissues.     

Inhibition of rat liver and kidney arginase by cadmium ion

Cadmium ion activates arginase from many species of organisms but is an inhibitor of arginase from many other species. The purpose of this study was to investigate the inhibition of rat liver and kidney arginase by cadmium ion. Rat kidney arginase was inhibited by much lower concentrations of cadmium ion than rat liver arginase. Cadmium ion was a mixed noncompetitive inhibitor of both rat liver and kidney arginase. Cadmium ion enhanced the substrate activation of rat kidney arginase while still inhibiting the enzyme. Cadmium ion prevented the substrate inhibition of rat kidney arginase by fluoride while still inhibiting the enzyme. Cadmium ion also inhibited rat kidney arginase in the presence of manganese ion.     

Studies on L-arginase in developing rat small intestine, brain, and kidney. I. Ontogenic evolution of arginase isoenzymes

The adult patterns of arginase isoenzymes in rat intestine, kidney, and brain are nearly identical and consist of two forms, cationic A1 and anionic A4. In this paper, the organ-specific maturation of the enzyme equipment in these tissues is reported. The activity of arginase in all tissues studied could be detected on the 13th to 16th days of gestation. In fetal intestine and kidney the arginase activity is low, and persists up to the weaning time when the rapid, 10-fold rise of the enzyme activity occurs. However, the adult pattern of arginase isoenzymes in these tissues is accomplished in different ways. In the intestine, arginase A1 appears in fetal life and is the only form of the enzyme till the 19th to 21st days of postnatal life when the second form of arginase, A4, appears and rapidly accumulates, being exclusively responsible for the rise of the total enzyme activity at the time of weaning. In kidney, arginase A1 alone is present in the early fetal period. Arginase A4 appears 3-4 days before birth and its activity persists unchanged within the first 2 weeks of postnatal life. The intensive rise in total specific activity of kidney arginase at weaning is due to the accumulation of preexisting arginase A4. In brain, the adult pattern of arginase isoenzymes is achieved earlier than in other tissues. Both forms, A1 and A4, occur on Days 13-14 of gestation.     

Purification of rat kidney arginases A1 and A4 and their subcellular distribution

Arginase A1 and arginase A4 were isolated from rat kidney. Arginase A4, which is the main form of arginase in rat kidney, was obtained at a highly purified preparation; its specific activity was 1057 mumoles ornithine . min-1 . mg-1 protein. The two forms differed in subcellular localization. Form A1 was restricted to the cytosol while form A4 occurred mainly in the mitochondrial matrix. Kidney arginases A1 and A4 were found to differ in immunological properties. Kidney arginase A1, in contrast to arginase A4, precipitated with antibodies against arginase A1 from rat liver. Arginase A1 from kidney was shown to differ from arginase A1 from the liver. The two enzymes could be distinguished by double diffusion test and immunoelectrophoresis.     

Assay and kinetics of arginase

A sensitive colorimetric assay for arginase was developed. Urea produced by arginase was hydrolyzed to ammonia by urease, the ammonia was converted to indophenol, and the absorbance was measured at 570 nm. The assay is useful with low concentrations of arginase (0.5 munit or less than 1 ng rat liver arginase) and with a wide range of arginine concentrations (50 microM to 12.5 mM). Michaelis-Menten kinetics and a Km for arginine of 1.7 mM were obtained for Mn2+-activated rat liver arginase; the unactivated enzyme did not display linear behavior on double-reciprocal plots. The kinetic data for unactivated arginase indicated either negative cooperativity or two types of active sites on the arginase tetramer with different affinities for arginine. The new assay is particularly well suited for kinetic studies of activated and unactivated arginase.     

Purification of a soluble ATPase from rat liver mitochondria by AMP-Sepharose affinity chromatography.

ATPase (ATP phosphohydrolase, EC 3.6.1.3) activity was shown in the soluble fraction of rat liver micochondria. Two molecular forms (ATPase 1 and 2) were isolated. ATPase 1 has already been studied. The present paper deals with the purification method of ATPase 2 which was achieved by the following steps: (NH4)2SO4 precipitation. DEAE-cellulose chromatography, hydroxyapatite chromatography, Sephadex G100 filtration and AMP-Sepharose affinity chromatography. The purified protein was characterized by bidimensional polyacrylamide gel electrophoresis. Molecular weight evaluated by SDS-polyacrylamide gel electrophoresis and Sephadex G100 gel filtration was found to be 61 500 +/- 3000.     

Chemical modification of rat liver arginase

Chemical modifications were used to search for catalytically important residues of rat liver arginase. The results of carbamoylation, nitration and diazotization suggest that lysyl and tyrosyl residues are not involved in the catalytic function of arginase. The modification of 5--6 tryptophanyl residues by N-bromosuccinimide or 2-hydroxy-5-nitrobenzyl bromide led to about 90% inhibition of the enzyme activity. Photooxidation of 21 histydyl residues also led to considerable inactivation of arginase. The modification of tryptophanyl and histidyl residues did not cause dissociation of the enzyme into subunits.     

Purification and properties of arginase of rat kidney

l-Arginase from rat kidney was partially purified and some properties were compared with those of l-arginase of rat liver. The kidney enzyme was firmly bound to the mitochondrial fraction and after solubilization required arginine or an unknown factor in tissue extracts for stabilization after dialysis. The two enzymes differed also in stability with respect to acetone treatment, heating or freezing. In further contrast with liver arginase, arginase from kidney was not adsorbed to CM-cellulose at pH7.5 and its activity was not increased by incubation with Mn(2+). Other differences were seen in relative specificities for substrates, ratio of hydrolysis rates with high and low concentrations of arginine and effects of certain inhibitors. Antisera prepared to pure liver arginase did not cross-react with partially purified kidney arginase.     

Cloning and expression in Escherichia coli of cDNA for arginase of rat liver

A cDNA expression library constructed in a plasmid pUC8 from poly(A)+ RNA of rat liver was screened immunologically, using an antibody against arginase of rat liver. A cDNA clone was isolated and identified by hybrid-selected translation. The clone contained an insert approximately 1.35 kilobase pairs in length. In the bacterial clone, we detected a specific protein of Mr = about 43,000 that is slightly larger than the purified arginase (Mr = about 40,000) and a high activity of arginase was expressed. The arginase mRNA species of about 1600 bases long was detected in the liver, but not in the small intestine, kidney, spleen and heart of the rats.     

Purification of rat pancreatic lipase

A procedure for the isolation of lipase (glycerolester hydrolase, EC 3.1.1.3) from rat pancreas is described. The purification scheme includes homogenization of the pancreas, centrifugation at 3,000 rpm, centrifugation at 40,000 rpm, DEAE-cellulose chromatography, precipitation of amylase as the amylase-glycogen complex, gel filtration of the amylase-free proteins on Sephadex G-100, and chromatography on carboxymethyl-Sephadex C-50. The enzyme showed only one band on polyacrylamide gel electrophoresis and had a specific activity of 5330 +/- 80 units/mg of protein.