Qualitative and quantitative abnormalities of argininosuccinate synthetase in citrullinemia

doi:10.1016/0009-8981(81)90318-1

Clinica Chimica Acta

Volume 109, Issue 3, 5 February 1981, Pages 325-335

https://doi.org/10.1016/0009-8981(81)90318-1 Get rights and content

Abstract

Enzymological and immunochemical analyses of the liver were performed in seven Japanese patients with citrullinemia.

Among the urea cycle enzymes in the liver, only the activity of argininosuccinate synthetase was specifically decreased to 2 to 50% of normal controls. Liver argininosuccinate synthetase of patients was indistinguishable from that of controls when tested immunochemically by Ouchterlony's double immunodiffusion technique with anti-rat argininosuccinate synthetase antiserum. Immunochemical analysis by means of the single radial immunodiffusion revealed that the decrease in the activity of liver argininosuccinate synthetase was explainable by a decrease in the amount of the enzyme protein in five patients, while the decrease in the activity in the other two patients was not accompanied by a decrease of enzyme protein.

The K_m values for the substrates of liver argininosuccinate synthetase of the former five were similar to those of the control, while the kinetic properties of the latter two were quite different in terms of higher K_m values and negative cooperativity.

From these results, we consider that citrullinemia may consist of more than one type including qualitative or quantitative abnormalities of argininosuccinate synthetase caused by some defects in certain genes or in the epigenetic processes in the liver.

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Cited by (85)

mRNA Therapy Improves Metabolic and Behavioral Abnormalities in a Murine Model of Citrin Deficiency
2019, Molecular Therapy
Citation Excerpt :
In humans, citrin deficiency causes accumulation of citrulline in the liver and plasma and subsequent failure of the urea cycle to efficiently clear ammonia from the blood stream, resulting in hyperammonemia.1 It is believed that the accumulation of citrulline in CTLN2 patients is caused by two possible mechanisms: (1) unavailability of Asp as a substrate for ASS and (2) loss of ASS protein.5,6 Unlike the classic neonatal and infantile type I citrullinemia (CTLN1), which is caused by deficiency of the ASS gene, CTLN2 is clinically characterized by adult-onset features such as serious and recurring hyperammonemia and associated neurological symptoms, including disorientation, delusion, unconsciousness, seizures, hypersensitivity, and coma.3,7
Citrin deficiency is an autosomal recessive disorder caused by loss-of-function mutations in SLC25A13, encoding the liver-specific mitochondrial aspartate/glutamate transporter. It has a broad spectrum of clinical phenotypes, including life-threatening neurological complications. Conventional protein replacement therapy is not an option for these patients because of drug delivery hurdles, and current gene therapy approaches (e.g., AAV) have been hampered by immunogenicity and genotoxicity. Although dietary approaches have shown some benefits in managing citrin deficiency, the only curative treatment option for these patients is liver transplantation, which is high-risk and associated with long-term complications because of chronic immunosuppression. To develop a new class of therapy for citrin deficiency, codon-optimized mRNA encoding human citrin (hCitrin) was encapsulated in lipid nanoparticles (LNPs). We demonstrate the efficacy of hCitrin-mRNA-LNP therapy in cultured human cells and in a murine model of citrin deficiency that resembles the human condition. Of note, intravenous (i.v.) administration of the hCitrin-mRNA resulted in a significant reduction in (1) hepatic citrulline and blood ammonia levels following oral sucrose challenge and (2) sucrose aversion, hallmarks of hCitrin deficiency. In conclusion, mRNA-LNP therapy could have a significant therapeutic effect on the treatment of citrin deficiency and other mitochondrial enzymopathies with limited treatment options.
A novel mutation of the SLC25A13 gene in a Chinese patient with citrin deficiency detected by target next-generation sequencing
2014, Gene
Citation Excerpt :
Type II citrullinaemia, also known as citrin deficiency, has two major clinical phenotypes: adult-onset type II citrullinaemia (CTLN2; OMIM# 603471) and neonatal intrahepatic cholestatic hepatitis caused by citrin deficiency (NICCD; OMIM# 605814) (Saheki and Kobayashi, 2002). Adult-onset type II citrullinaemia is clinically characterised by the sudden onset of various neuropsychological symptoms such as disorientation, abnormal behaviour, convulsions, delusions, hallucinations and brief coma due to hyperammonaemia (Saheki et al., 1981, 1987). In some cases, rapid progression can lead to brain oedema, and death is possible if liver transplantation is not implemented (Yasuda et al., 2000).
Type II citrullinaemia, also known as citrin deficiency, is an autosomal recessive metabolic disorder, which is caused by pathogenic mutations in the SLC25A13 gene on chromosome 7q21.3. One of the clinical manifestations of type II citrullinaemia is neonatal intrahepatic cholestatic hepatitis caused by citrin deficiency (NICCD, OMIM# 605814). In this study, a 5-month-old female Chinese neonate diagnosed with type II citrullinaemia was examined. The diagnosis was based on biochemical and clinical findings, including organic acid profiling using a gas chromatography mass spectrometry (GC/MS), and the patient's parents were unaffected. Approximately 14 kb of the exon sequences of the SLC25A13 and two relative genes (ASS1 and FAH) from the proband and 100 case-unrelated controls were captured by array-based capture method followed by high-throughput next-generation sequencing. Two single-nucleotide mutations were detected in the proband, including the previous reported c.1177+1G>A mutation and a novel c.754G>A mutation in the SLC25A13 gene. Sanger sequence results showed that the patient was a compound heterozygote for the two mutations. The novel mutation (c.754G>A), which is predicted to affect the normal structure and function of citrin, is a candidate pathogenic mutation. Target sequence capture combined with high-throughput next-generation sequencing technologies is proven to be an effective method for molecular genetic testing of type II citrullinaemia.
Citrin/mitochondrial glycerol-3-phosphate dehydrogenase double knock-out mice recapitulate features of human citrin deficiency
2007, Journal of Biological Chemistry
Citation Excerpt :
Plasma triglycerides (TG; TG-II Kainos; Kainos Laboratories, Inc., Tokyo, Japan), free fatty acids (FFA; Determiner-NEFA; Kyowa Medix Co. Ltd., Tokyo, Japan), total cholesterol (Cholesterol E-test Wako), glycerol (GLY 105; Randox Laboratories, Antrim, UK), ketone bodies (Ketone Test Sanwa; Sanwa Kagaku Kenkyusho, Nagoya, Japan), bile acid (Bile Acid Test Wako), Asp aminotransferase (TA-LN Kainos), alanine aminotransferase (TA-LN Kainos), and alkaline phosphatase (K-test Wako) were determined with commercially available kits as indicated, respectively. Determination of Urea Cycle Enzyme Activities—Liver extracts were prepared as described previously (46). The urea cycle enzyme activities were determined using the methods of Schimke (47) for carbamoyl-phosphate synthetase, Pierson et al. (48) for ornithine carbamoyltransferase, Su et al. (49) for argininosuccinate synthetase and argininosuccinate lyase, and Ruegg et al. (50) for arginase.
Citrin is the liver-type mitochondrial aspartate-glutamate carrier that participates in urea, protein, and nucleotide biosynthetic pathways by supplying aspartate from mitochondria to the cytosol. Citrin also plays a role in transporting cytosolic NADH reducing equivalents into mitochondria as a component of the malate-aspartate shuttle. In humans, loss-of-function mutations in the SLC25A13 gene encoding citrin cause both adult-onset type II citrullinemia and neonatal intrahepatic cholestasis, collectively referred to as human citrin deficiency. Citrin knock-out mice fail to display features of human citrin deficiency. Based on the hypothesis that an enhanced glycerol phosphate shuttle activity may be compensating for the loss of citrin function in the mouse, we have generated mice with a combined disruption of the genes for citrin and mitochondrial glycerol 3-phosphate dehydrogenase. The resulting double knock-out mice demonstrated citrullinemia, hyperammonemia that was further elevated by oral sucrose administration, hypoglycemia, and a fatty liver, all features of human citrin deficiency. An increased hepatic lactate/pyruvate ratio in the double knock-out mice compared with controls was also further elevated by the oral sucrose administration, suggesting that an altered cytosolic NADH/NAD⁺ ratio is closely associated with the hyperammonemia observed. Microarray analyses identified over 100 genes that were differentially expressed in the double knock-out mice compared with wild-type controls, revealing genes potentially involved in compensatory or downstream effects of the combined mutations. Together, our data indicate that the more severe phenotype present in the citrin/mitochondrial glycerol-3-phosphate dehydrogenase double knock-out mice represents a more accurate model of human citrin deficiency than citrin knock-out mice.
Metabolic derangements in deficiency of citrin, a liver-type mitochondrial aspartate-glutamate carrier
2005, Hepatology Research
Citrin, encoded by SLC25A13, is a liver-type mitochondrial aspartate-glutamate carrier (AGC), of which deficiency, in autosomal recessive trait, causes neonatal intrahepatic cholestasis (NICCD) and adult-onset type II citrullinemia (CTLN2). NICCD patients have jaundice, hypoproteinemia, hypoglycemia, galactosemia, growth retardation, fatty liver and multiple aminoacidemia including citrulline, methionine, threonine and tyrosine.
Some of the neonates who have experienced NICCD suffer from severe CTLN2 more than 10 years or several decades later. In CTLN2, neuropsychotic symptoms such as disorientation, aberrant behavior, coma and death are observed. Laboratory findings reveal hyperammonemia, citrullinemia, fatty liver and liver-specific decrease in a urea cycle enzyme, argininosuccinate synthetase (ASS). In some cases, hyperlipidemia, pancreatitis and hepatoma are accompanied with CTLN2. Citrin as a liver-type AGC plays a role in supplying aspartate to the cytosol for urea, protein and nucleotide synthesis by exchanging mitochondrial aspartate for cytosolic glutamate and proton, and transporting cytosolic NADH reducing equivalent to mitochondria as a member of malate aspartate shuttle essential for aerobic glycolysis. AGC is also important for gluconeogenesis from lactate.
Although it is difficult to explain pathogenesis of the symptoms such as cholestasis in NICCD and liver-specific decrease of ASS protein in CTLN2 from the functions of the AGC, some are understandable by the loss of citrin functions. Many CTLN2 patients have been treated with a low protein and high carbohydrate diet and glycerol at the hyperammonemic coma. We argue that those treatments may result in fatty liver, hyperlipidemia, hyperammonemia and even death due to loss of the citrin functions.
Loss of citrin first cause deficiency of aspartate in the cytosol, which results in an increase in cytosolic NADH/NAD⁺ ratio and then activation of fatty acid synthesis pathway to compensate the aberrant ratio. This follows inhibition of fatty acid oxidation. The peculiar fondness for food of CTLN2 patients who like protein and dislike carbohydrate and sweets may be related to their metabolic requirements.
Adult-onset type II citrullinemia and idiopathic neonatal hepatitis caused by citrin deficiency: Involvement of the aspartate glutamate carrier for urea synthesis and maintenance of the urea cycle
2004, Molecular Genetics and Metabolism
Citrin is a mitochondrial aspartate glutamate carrier primarily expressed in the liver, heart, and kidney. We found that adult-onset type II citrullinemia is caused by mutations in the SLC25A13 gene that encodes for citrin. In this report, we describe the frequency of SLC25A13 mutations, the roles of citrin as a member of the urea cycle and as a member of the malate–aspartate shuttle, the relationship between its functions and symptoms of citrin deficiency, and therapeutic issues.
Diagnosis and monitoring of inborn errors of metabolism using urease-pretreatment of urine, isotope dilution, and gas chromatography-mass spectrometry
2002, Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences
To diagnose inborn errors of metabolism, it would be desirable to simultaneously analyze and quantify organic acids, purines, pyrimidines, amino acids, sugars, polyols, and other compounds using a single-step fractionation; unfortunately, no such method currently exists. The present article will be concerned primarily with a practical yet comprehensive diagnostic procedure of inborn errors of metabolism (IEM). This procedure involves the use of urine or eluates from urine on filter paper, stable isotope dilution, and gas chromatography–mass spectrometry (GC–MS). This procedure not only offers reliable and quantitative evidence for diagnosing, understanding and monitoring the diseases, but also provides evidence for the diagnosis of new kinds of IEM. In this review, the differential diagnosis for hyperammonemia are described; deficiencies of ornithine carbamoyl transferase, argininosuccinate synthase (citrullinemia), argininosuccinate lyase and arginase, lysinuric protein intolerance, hyperammonemia–hyperornithinemia–homocitrullinemia syndrome, and citrullinemia type II. The diagnosis of IEM of purine and pyrimidine such as deficiencies of hypoxanthine–guanine phosphoribosyl transferase, adenine phosphoribosyl transferase, dihydropyrimidine dehydrogenase, dihydropyrimidinase and β-ureidopropionase are described. During the pilot study for newborn screening, we found neonates with diseases at a rate of 1 per 1400 including propionic acidemia, methylmalonic acidemia, orotic aciduria, β-ureidopropionase deficiency, lactic aciduria and neuroblastoma. A rapid and reliable prenatal diagnosis for propionic acidemia is also described.

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Qualitative and quantitative abnormalities of argininosuccinate synthetase in citrullinemia

Abstract

J. Pediatr.

J. Biol. Chem.

J. Biol. Chem.

Citrullinemia, a new amino aciduria associated with mental retardation

Lancet

Hereditary urea-cycle disorders

An autopsy case of juvenile hepato-cerebral degeneration (non-Wilsonian Inose-type) with mental retardation with special reference to amino acids metabolism

Psychiatr. Neurol. Jap.

Two young-age cases of the special form of hepatocerebral disease

Brain and Nerve

A report on two siblings with “pseudo-ulegyric type” of hepatocerebral disease

Brain and Nerve

Three cases of juvenile hepato-cerebral degeneration with citrullinemia

Brain and Nerve

A special form of hepatocerebral degeneration with citrullinemia

Neurol. Med.