Kidney Arginase Research Articles

Arginine Uptake by Chick Kidney Mitochondria

Arginine uptake by kidney mitochondria in two strains of chicks of high (HA) and low (LA) requirement of dietary arginine was studied by using an ion-exchange method. Dietary factors influencing uptake of arginine were also investigated. The results indicate that arginine uptake by kidney mitochondria of HA chicks was significantly higher than the LA chicks when arginine-deficient diet or diet with excess lysine was fed. The arginine uptake by kidney mitochondria reflects the kidney arginase activity. Both arginase activity and arginine uptake inversely correlated with growth rate of the two strains of chicks. However, the dietary factors that affect kidney mitochondria arginase activity are not completely parallel to the uptake of arginine by kidney mitochondria. A system that facilitates entry of arginine into kidney mitochondrial membrane is suggested.arginine uptake lysine uptake kidney mitochondria

Curcumin Improves Biomolecules Associated with Renal Function and Attenuates Oxidative Injury and Histopathological Changes in Potassium-Induced Toxicity in Rats' Kidney.

The protective effect of curcumin on potassium bromate (KBrO3)-induced renal damage was investigated in vivo. Treatment with KBrO3 (20mg/kgbw) caused a significant increase in arginase and adenosine deaminase (ADA) activities in rats' kidney. However, oral administration of curcumin (20mg/kg bw) caused a significant reduction in ADA and arginase activities in KBrO3 + CUR group. Furthermore, nitric oxide level was significantly low in KBrO3 group compared with the control. After treatment with curcumin in KBrO3 + CUR group, nitric oxide levels increased significantly (P < 0.05). Determination of some kidney biomarkers revealed elevated levels of creatinine, serum urea, and electrolytes (Na+ and Cl-) in KBrO3-treated rats. Curcumin effectively reduced the levels of these renal function parameters in KBrO3 + CUR groups and were not significantly different from the control. Antioxidant enzyme activities such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) activities as well as glutathione (GSH) levels were significantly low with concomitant higher levels of malondialdehyde (MDA) after treatment with KBrO3. Curcumin caused a significant increase in SOD, CAT, and GPX activities including GSH levels with lower production of MDA in kidney homogenates of rats in KBrO3 + CUR. Curcumin ameliorated corpuscular degeneration in the kidney tissue and exhibited protection against tubular necrosis. These results revealed the protective effect of curcumin against KBrO3-induced renal toxicity by preventing degradation of ADA and arginine, improving antioxidant status and histopathological changes in rats' kidney.

Determination of optimal conditions for activity of arginase in kidney of rabbit

Optimum conditions for arginase in kidney tissue may differ from those for arginase of liver. Because optimum conditions for measuring arginase activity in rabbit kidney tissue were not determined, it was aimed to optimize arginase of rabbit kidney tissue and compare it with arginase of liver. In the present study, the kidneys of six New Zealand rabbits aged 1 year old were used. It was found to be preincubation temperature 53 °C, preincubation period is 15 minutes, incubation period is 10 minutes and optimum pH is 10.1 in NaHCO3-NaOH buffer for arginase in rabbit kidney tissue. Enzyme achieved its highest activity at 1 mM MnCl2concentration. Km of arginase in rabbit kidney tissue for L-arginine was measured as 12.5 mM. It was determined that Mn+2 ions and preincubation at 53 °C were essential for the activation of the enzyme. As a result, optimal conditions for the kidney arginase were found to be different from those for the liver arginase. Our study indicates that arginases encoded by separate gene loci may have different optimal conditions

Effects of a chronic l-arginine supplementation on the arginase pathway in aged rats

While ageing is frequently associated with l-arginine deficiency, clinical and experimental studies provided controversial data on the interest of a chronic l-arginine supplementation with beneficial, no or even deleterious effects. It was hypothesized that these discrepancies might relate to a deviation of l-arginine metabolism towards production of l-ornithine rather than nitric oxide as a result of age-induced increase in arginase activity. This study investigated the effect of ageing on arginase activity/expression in target tissues and determined whether l-arginine supplementation modulated the effect of ageing on arginase activity. Arginase activity and expression were measured in the heart, vessel, brain, lung, kidney and liver in young rats (3-months old) and aged Wistar rats (22–24-months-old) with or without l-arginine supplementation (2.25% in drinking water for 6weeks). Plasma levels of l-arginine and l-ornithine were quantified in order to calculate the plasma l-arginine/l-ornithine ratio, considered as a reflection of arginase activity. Cardiovascular parameters (blood pressure, heart rate) and aortic vascular reactivity were also studied. Ageing dramatically reduced plasma l-arginine and l-arginine/l-ornithine ratio, decreased liver and kidney arginase activities but did not change activities in other tissues. l-Arginine supplementation normalized plasma l-arginine and l-arginine/l-ornithine ratio, improved endothelial function and decreased systolic blood pressure. These effects were associated with decreased arginase activity in aorta along with no change in the other tissues except in the lung in which activity was increased. A strong mismatch was therefore observed between arginase activity and expression in analyzed tissues. The present study reveals that ageing selectively changes arginase activity in clearance tissues, but does not support a role of the arginase pathway in the potential deleterious effect of the l-arginine supplementation in aged patients. Moreover, our data argue against the use of the measurement of plasma l-arginine/l-ornithine ratio to estimate arginase activity in aged patients.

Effects of Arginase Inhibition in Hypertensive Hyperthyroid Rats

This study analyzed the effects of chronic administration of N[omega]-hydroxy-nor-l-arginine (nor-NOHA), an inhibitor of arginase, on the hemodynamic, oxidative stress, morphologic, metabolic, and renal manifestations of hyperthyroidism in rats. Four groups of male Wistar rats were used: control, nor-NOHA-treated (10 mg/kg/day), thyroxine (T4)-treated (75 μg/rat/day), and thyroxine- plus nor-NOHA-treated rats. All treatments were maintained for 4 weeks. Body weight, tail systolic blood pressure (SBP), and heart rate (HR) were recorded weekly. Finally, morphologic, metabolic, plasma, and renal variables were measured. Arginase I and II protein abundance and arginase activity were measured in aorta, heart, and kidney. The T4 group showed increased arginase I and II protein abundance, arginase activity, SBP, HR, plasma nitrates/nitrites (NOx), brainstem and urinary isoprostanes, proteinuria and cardiac and renal hypertrophy in comparison to control rats. In hyperthyroid rats, chronic nor-NOHA prevented the increase in SBP and HR and decreased proteinuria in association with an increase in plasma NOx and a decrease in brainstem and urinary isoprostanes. In normal rats, nor-NOHA treatment did not significantly change any hemodynamic, morphologic, or renal variables. Acute nor-NOHA administration did not affect renal or systemic hemodynamic variables in normal or T4-treated rats. Hyperthyroidism in rats is associated with the increased expression and activity of arginase in aorta, heart, and kidney. Chronic arginase inhibition with nor-NOHA suppresses the characteristic hemodynamic manifestations of hyperthyroidism in association with a reduced oxidative stress. These results indicate an important role for arginase pathway alterations in the cardiovascular and renal abnormalities of hyperthyroidism.

Diabetic nephropathy is resistant to oral l-arginine or l-citrulline supplementation

Our recent publication showed that pharmacological blockade of arginases confers kidney protection in diabetic nephropathy via a nitric oxide (NO) synthase (NOS)3-dependent mechanism. Arginase competes with endothelial NOS (eNOS) for the common substrate L-arginine. Lack of L-arginine results in reduced NO production and eNOS uncoupling, which lead to endothelial dysfunction. Therefore, we hypothesized that L-arginine or L-citrulline supplementation would ameliorate diabetic nephropathy. DBA mice injected with multiple low doses of vehicle or streptozotocin (50 mg/kg ip for 5 days) were provided drinking water with or without L-arginine (1.5%, 6.05 g·kg(-1)·day(-1)) or L-citrulline (1.66%, 5.73 g·kg(-1)·day(-1)) for 9 wk. Nonsupplemented diabetic mice showed significant increases in albuminuria, blood urea nitrogen, glomerular histopathological changes, kidney macrophage recruitment, kidney TNF-α and fibronectin mRNA expression, kidney arginase activity, kidney arginase-2 protein expression, and urinary oxidative stress along with a significant reduction of nephrin and eNOS protein expression and kidney nitrite + nitrate compared with normal mice after 9 wk of diabetes. Surprisingly, L-arginine or L-citrulline supplementation in diabetic mice did not affect any of these parameters despite greatly increasing kidney and plasma arginine levels. These findings demonstrate that chronic L-arginine or L-citrulline supplementation does not prevent or reduce renal injury in a model of type 1 diabetes.

Arginase-2 mediates diabetic renal injury.

OBJECTIVETo determine 1) whether renal arginase activity or expression is increased in diabetes and 2) whether arginase plays a role in development of diabetic nephropathy (DN).RESEARCH DESIGN AND METHODSThe impact of arginase activity and expression on renal damage was evaluated in spontaneously diabetic Ins2Akita mice and in streptozotocin (STZ)-induced diabetic Dilute Brown Agouti (DBA) and arginase-2–deficient mice (Arg2−/−).RESULTSPharmacological blockade or genetic deficiency of arginase-2 conferred kidney protection in Ins2Akita mice or STZ-induced diabetic renal injury. Blocking arginases using S-(2-boronoethyl)-l-cysteine for 9 weeks in Ins2Akita mice or 6 weeks in STZ-induced diabetic DBA mice significantly attenuated albuminuria, the increase in blood urea nitrogen, histopathological changes, and kidney macrophage recruitment compared with vehicle-treated Ins2Akita mice. Furthermore, kidney arginase-2 expression increased in Ins2Akita mice compared with control. In contrast, arginase-1 expression was undetectable in kidneys under normal or diabetes conditions. Arg2−/− mice mimicked arginase blockade by reducing albuminuria after 6 and 18 weeks of STZ-induced diabetes. In wild-type mice, kidney arginase activity increased significantly after 6 and 18 weeks of STZ-induced diabetes but remained very low in STZ-diabetic Arg2−/− mice. The increase in kidney arginase activity was associated with a reduction in renal medullary blood flow in wild-type mice after 6 weeks of STZ-induced diabetes, an effect significantly attenuated in diabetic Arg2−/− mice.CONCLUSIONSThese findings indicate that arginase-2 plays a major role in induction of diabetic renal injury and that blocking arginase-2 activity or expression could be a novel therapeutic approach for treatment of DN.

Expression and function of arginine-producing and consuming-enzymes in the kidney

The kidney plays a key role in arginine metabolism. Arginine production is controlled by argininosuccinate synthetase (ASS) and argininosuccinate lyase (ASL) which metabolize citrulline and aspartate to arginine and fumarate whereas arginine consumption is dependent on arginine:glycine amidinotransferase (GAT), which mediates creatine and ornithine synthesis. Histological and biochemical techniques have been used to study the distribution and activity of these enzymes in anatomically dissected segments, in isolated fragments of tubules and in whole tissues. ASS and ASL mRNAs and proteins are expressed in the proximal tubule. Within this nephron segment, the proximal convoluted tubule has a higher arginine synthesis capacity than the proximal straight tubules. Furthermore, this arginine-synthesizing portion of the nephron matches perfectly with the site of citrulline reabsorption from the glomerular filtrate. The kidney itself can produce citrulline from methylated arginine, but this capacity is limited. Therefore, intestinal citrulline synthesis is required for renal arginine production. Although the proximal convoluted tubule also expresses a significant amount of GAT, only 10% of renal arginine synthesis is metabolized to guanidinoacetic acid, possibly because GAT has a mitochondrial localization. Kidney arginase (AII) is expressed in the cortical and outer medullary proximal straight tubules and does not degrade significant amounts of newly synthesized arginine. The data presented in this review identify the proximal convoluted tubule as the main site of endogenous arginine biosynthesis.

Cocoa flavanols lower vascular arginase activity in human endothelial cells in vitro and in erythrocytes in vivo

The availability of l-arginine can be a rate-limiting factor for cellular NO production by nitric oxide synthases (NOS). Arginase competes with NOS for l-arginine as the common substrate. Increased arginase activity has been linked to low NO levels, and an inhibition of arginase activity has been reported to improve endothelium-dependent vasorelaxation. Based on the above, we hypothesized that an increase in the circulating NO pool following flavanol consumption could be correlated with decreased arginase activity. To test this hypothesis we (a) investigated the effects of (−)-epicatechin and its structurally related metabolites on endothelial arginase expression and activity in vitro; (b) evaluated the effects of dietary flavanol-rich cocoa on kidney arginase activity in vivo; and (c) assessed human erythrocyte arginase activity following flavanol-rich cocoa beverage consumption in a double-blind intervention study with cross-over design. The results demonstrate that cocoa flavanols lower arginase-2 mRNA expression and activity in HUVEC. Dietary intervention with flavanol-rich cocoa caused diminished arginase activity in rat kidney and, erythrocyte arginase activity was lowered in healthy humans following consumption of a high flavanol beverage in vivo.

Arginase induction by sodium phenylbutyrate in mouse tissues and human cell lines

Hyperargininemia is a urea cycle disorder caused by mutations in the gene for arginase I (AI) resulting in elevated blood arginine and ammonia levels. Sodium phenylacetate and a precursor, sodium phenylbutyrate (NaPB) have been used to lower ammonia, conjugating glutamine to produce phenylacetylglutamine which is excreted in urine. The elevated arginine levels induce the second arginase (AII) in patient kidney and kidney tissue culture. It has been shown that NaPB increases expression of some target genes and we tested its effect on arginase induction. Eight 9-week old male mice fed on chow containing 7.5 g NaPB/kg rodent chow and drank water with 10 g NaPB/L, and four control mice had a normal diet. After one week all mice were sacrificed. The arginase specific activities for control and NaPB mice, respectively, were 38.2 and 59.4 U/mg in liver, 0.33 and 0.42 U/mg in kidney, and 0.29 and 1.19 U/mg in brain. Immunoprecipitation of arginase in each tissue with AI and AII antibodies showed the activity induced by NaPB is mostly AI. AII may also be induced in kidney. AI accounts for the fourfold increased activity in brain. In some cell lines, NaPB increased arginase activity up to fivefold depending on dose (1–5 mM) and exposure time (2–5 days); control and NaPB activities, respectively, are: erythroleukemia, HEL, 0.06 and 0.31 U/mg, and K562, 0.46 and 1.74 U/mg; embryonic kidney, HEK293, 1.98 and 3.58 U/mg; breast adenocarcinoma, MDA-MB-468, 1.11 and 4.06 U/mg; and prostate adenocarcinoma, PC-3, 0.55 and 3.20 U/mg. In MDA-MB-468 and HEK most, but not all, of the induced activity is AI. These studies suggest that NaPB may induce AI when used to treat urea cycle disorders. It is relatively less useful in AI deficiency, although it could have some effect in those patients with missense mutations.

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.

Evaluation of optimal conditions for arginase activity in streptozotocin induced diabetic rats

The assay conditions needed to achieve maximal activity of liver and kidney arginase in diabetic and non-diabetic rats were investigated and compared. The physicochemical and kinetic properties of liver arginase in diabetic and control rats were very similar, those of kidney arginase were significantly different. It was found that preincubation temperature (68&amp;deg;C), preincubation period (20 min), optimum pH (10.1) of liver arginase and K&lt;sub&gt;m&lt;/sub&gt; (3.2) for its substrate, L-arginine, did not change in diabetic and non-diabetic rats. As a consequence of diabetes, the optimum Mn&lt;sup&gt;2+&lt;/sup&gt; concentration for liver arginase only changed from 1 to 2 mM. Although the preincubation temperature and period for activation of kidney arginase in control rats was unnecessary, they were found to be 56&amp;ordm;C and 12 min in diabetic rats. The pH profile of arginase in kidney of diabetic rats was different from that of control rats. The K&lt;sub&gt;m&lt;/sub&gt; value (6.7) of arginase for L-arginine in kidney is unchanged in diabetes whereas a marked decrease in V&lt;sub&gt;max&lt;/sub&gt; was found. Optimum Mn&lt;sup&gt;2+&lt;/sup&gt; concentration (2 mM) for kidney arginase was unchanged in diabetes. The activity of arginase in liver of diabetic animals was higher 1.5 to 1.7 times than that of controls. Diabetes caused an about 53% decrease of arginase activity in kidney of female rats, 26% in that of males. These findings may suggest an idea that encoded arginases by separate gene loci may be affected differently by the pathological and hormonal status.

Structure and Function of Arginases

The arginases catalyze the divalent cation dependent hydrolysis of L-arginine to produce L-ornithine and urea. Although traditionally considered in terms of its role as the final enzyme of the urea cycle, the enzyme is found in a variety of nonhepatic tissues. These findings suggest that the enzyme may have other functions in addition to its role in nitrogen metabolism. High-resolution crystal structures have been determined for recombinant rat liver (type I) arginase and for recombinant human kidney (type II) arginase, their variants, and complexes with products and inhibitors. Each identical subunit of the trimeric enzyme contains an active site that lies at the bottom of a 15 A deep cleft. The 2 essential Mn(II) ions are located at the bottom of this cleft, separated by approximately 3.3 A and bridged by oxygens derived from 2 aspartic acid residues and a solvent-derived hydroxide. This metal bridging hydroxide is proposed to be the nucleophile that attacks the guanidinium carbon of substrate arginine. On the basis of this proposed mechanism, boronic acid inhibitors of the enzyme have been synthesized and characterized kinetically and structurally. These inhibitors display slow-onset inhibition at the pH optimum of the enzyme, and are found as tetrahedral species at the active site, as determined by X-ray diffraction. The potent inhibition of arginases I and II by these compounds has not only delineated key enzyme-substrate interactions, but has also led to a greater understanding of the role of arginase in nonhepatic tissues.

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.

Decreased expression of arginase II in the kidneys of Dahl salt-sensitive rats.

Arginase catalyzes the hydrolysis of arginine to urea and ornithine. Urea is not only an important solute for concentrating urine but also inhibits Na-K-2Cl cotransport. To elucidate the roles of arginase in the development of salt-sensitive hypertension, we examined arginase activity and expression in the kidney and other organs of Dahl/Rapp salt-sensitive (SS) and salt-resistant (SR) rats before and after 4 weeks' administration of a 4% NaCl or control diet. At 4 weeks of age, arginase activity in the kidney was lower in SS rats than in SR rats. Kidney arginase activity was lower in SS rats than in SR rats at 8 weeks of age, and salt loading did not alter arginase activity. Arginase II (the dominant isoform in the kidney) mRNA and protein in the kidney of salt-loaded SS rats were also lower than those of salt-loaded SR rats. Arginase activities in the liver and cerebellum did not differ between SS and SR rats. To examine the effect of urea, the product of arginase reaction, on the development of hypertension, SS rats were given a 4% NaCl diet containing 5% kaolin or 5% urea. Six-week urea supplementation attenuated the development of hypertension in SS rats. These findings suggest that decreased arginase expression in the kidney may be at least partially responsible for the salt-sensitive hypertension in SS rats.

Plasma Levels of Arginine, Ornithine, and Urea and Growth Performance of Broilers Fed Supplemental L-Arginine During Cool Temperature Exposure

Two experiments (Experiment 1 and 2) were conducted to evaluate growth performance, ascites mortality, and concentrations of plasma Arg, urea, and ornithine in male broilers raised in floor pens (2 × 4 factorial experiment, six pens for treatment) and exposed to cool temperatures averaging 16 C after 21 d of age. Broilers were fed low- or high-CP diets in both Experiments. In Experiment 1, Arg treatments consisted of control (no supplemental Arg); 0.15 or 0.3% supplemental Arg in the diet (low- and medium-Arg feed, respectively); and 0.3% supplemental Arg in the drinking water (Arg-water). Arginine levels were increased in Experiment 2 and consisted of the following: control (no supplemental Arg); 0.3 or 0.85% supplemental Arg in the diet (medium- and high-Arg feed, respectively); and 0.6% supplemental Arg in the drinking water (Arg-water). The water treatment followed a 3-d cyclic regimen, with supplemental Arg being provided for 24 h, followed by tap water for 48 h. When the broilers reached 37 d of age and all groups had consumed tap water for the previous 48 h, blood samples were collected from one bird per pen (Time 0, 0700 h); then supplemental Arg was provided in the Arg-water group, and additional blood samples were collected from the control and Arg-water groups at 3, 6, 12, and 36 h after Time 0. Plasma amino acids were analyzed using HPLC. Birds fed the high-CP diet were heavier at 49 d than birds fed the low-CP diet in Experiment 1, but not in Experiment 2. No differences were found in feed conversion or ascites mortality due to CP or Arg treatments in either experiment. In both experiments, plasma Arg was similar for all groups at Time 0, but increased in the Arg-water group at 3, 6, and 12 h after Arg was provided in the water. Within 12 h after returning to tap water, plasma Arg levels of the Arg-water group did not differ from the control group. Plasma urea and ornithine were parallel to plasma Arg concentrations, and the high-CP diets resulted in higher plasma levels of urea and ornithine compared with low-CP diets. These results indicate that kidney arginase was readily activated by Arg provided in the water, resulting in an immediate increase in plasma urea and ornithine. Plasma Arg was increased significantly, but no effects were observed in ascites mortality.

Comparison of the inhibition of rat liver and kidney arginase by metal ions

Comparison of the inhibition of rat liver and kidney arginase by metal ions

L-Canavanine Influences Feed Intake, Plasma Basic Amino Acid Concentrations and Kidney Arginase Activity in Chicks

L-Canavanine [2-amino-4-(guanidinooxy) butyric acid], a non-protein amino acid that is structurally analogous to arginine, has been proposed as a major antinutritional factor responsible for the toxic effects induced by raw Canavalia ensiformis (L.) seeds in chicks. We investigated the effects of L-canavanine on performance and select metabolic responses of growing chicks. Canavanine was added to a control diet, in an amount equivalent to that provided by 300 g raw canavalia seeds/kg diet (10 g free base canavanine/kg diet). Growth, plasma basic amino acids and kidney arginase, activity were measured. The incorporation of canavanine into a nutritionally balanced diet for growing chicks depressed feed intake and growth by approximately 25% (P < 0.01) compared with the control diet. Performance was unaffected by equimolar amounts of arginine. Canavanine exerted its growth-depressing effect exclusively by reducing feed intake, because this effect was not observed in a pair-feeding experiment. Chicks fed a diet containing 473 mmol canavanine sulfate/kg for 11 d were given an intracrop dose of 946 mmol of canavanine sulfate or arginine hydrochloride. In both cases, plasma histidine and lysine concentrations were significantly decreased compared with a placebo group dosed with water. Plasma arginine concentration was unaffected by the canavanine sulfate dose but, as expected, was significantly increased by the arginine hydrochloride dose. Free base canavanine significantly (P < 0.05) reduced kidney arginase activity. No overt toxic effects were observed at any point during the study. These data indicate that, although canavanine is not the principal antinutritional factor in Canavalia ensiformis seeds, its presence in the diet precludes optimum performance of chicks.

Nonidentity of subunits of human kidney arginase A1 and human liver arginase A5.

The main forms of arginase A1 from human kidney and A5 from human liver were purified to homogeneity. Molecular weight of both forms of enzyme approximates 120,000. In the presence of EDTA these arginases dissociate into single type distinct subunits. M(r) of both kinds of subunits is 30,000. Similarly as native arginase forms, they differ in electric charge and display complete immunological incompatibility.

Isolation of human liver arginase cdna and demonstration of nonhomology between the two human arginase genes

A human liver cDNA library was screened by colony hybridization with a rat liver arginase cDNA. The number of positive clones detected was in agreement with the estimated abundance of arginase message in liver, and the identities of several of these clones were verified by hybrid-select translation, immunoprecipitation, and competition by purified arginase. The largest of these human liver arginase cDNAs was then used to detect arginase message on northern blots at levels consistent with the activities of liver arginase in the tissues and cells studied. The absence of a hybridization signal with mRNA from a cell line expressing only human kidney arginase demonstrated the lack of homology between the two human arginase genes and indicated considerable evolutionary divergence between these two loci.