Publications

• Kinetic mutations in argininosuccinate synthetase deficiency: characterisation and in vitro correction by substrate supplementation.

  Diez-Fernandez C., Wellauer O., Gemperle C., Ruefenacht V., Fingerhut R., Haeberle J.

  <h4>Background</h4>Citrullinemia type 1 is an autosomal-recessive urea cycle disorder caused by mutations in the ASS1 gene and characterised by increased plasma citrulline concentrations. Of the ∼90 argininosuccinate synthetase (ASS) missense mutations reported, 21 map near the substrate (aspartat ... >> More

  <h4>Background</h4>Citrullinemia type 1 is an autosomal-recessive urea cycle disorder caused by mutations in the ASS1 gene and characterised by increased plasma citrulline concentrations. Of the ∼90 argininosuccinate synthetase (ASS) missense mutations reported, 21 map near the substrate (aspartate or citrulline) binding site, and thus are potential kinetic mutations whose decreased activities could be amenable to substrate supplementation. This article aims at characterising these 21 ASS mutations to prove their disease-causing role and to test substrate supplementation as a novel therapeutic approach.<h4>Methods</h4>We used an Escherichia coli expression system to study all potentially kinetic ASS mutations. All mutant enzymes were nickel-affinity purified, their activity and kinetic parameters were measured using tandem mass spectrometry and their thermal stability using differential scanning fluorimetry. Structural rationalisation of the effects of these mutations was performed.<h4>Results</h4>Of the characterised mutants, 13 were totally inactive while 8 exhibited decreased affinity for aspartate and citrulline. The activity of these eight kinetic mutations could be rescued to ∼10-99% of the wild-type using high l-aspartate concentrations.<h4>Conclusions</h4>Substrate supplementation raised in vitro the activity of eight citrullinemia type 1 mutations with reduced affinity for aspartate. As a direct translation of these results to the clinics, we propose to further evaluate the use of oxaloacetate, a nitrogen-free aspartate precursor and already available medical food (anti-ageing and brain stimulating, not considered as a drug by the US Food and Drug Administration), in patients with citrullinemia type 1 with decreased aspartate affinity. Although only patients with kinetic mutations would benefit, oxaloacetate could offer a safe novel treatment. << Less

  J. Med. Genet. 53:710-719(2016) [PubMed] [EuropePMC]

• Arginine inhibits the arginine biosynthesis rate-limiting enzyme and leads to the accumulation of intracellular aspartate in Synechocystis sp. PCC 6803.

  Katayama N., Osanai T.

  Cyanobacteria are oxygen-evolving photosynthetic prokaryotes that affect the global carbon and nitrogen turnover. Synechocystis sp. PCC 6803 (Synechocystis 6803) is a model cyanobacterium that has been widely studied and can utilize and uptake various nitrogen sources and amino acids from the oute ... >> More

  Cyanobacteria are oxygen-evolving photosynthetic prokaryotes that affect the global carbon and nitrogen turnover. Synechocystis sp. PCC 6803 (Synechocystis 6803) is a model cyanobacterium that has been widely studied and can utilize and uptake various nitrogen sources and amino acids from the outer environment and media. l-arginine is a nitrogen-rich amino acid used as a nitrogen reservoir in Synechocystis 6803, and its biosynthesis is strictly regulated by feedback inhibition. Argininosuccinate synthetase (ArgG; EC 6.3.4.5) is the rate-limiting enzyme in arginine biosynthesis and catalyzes the condensation of citrulline and aspartate using ATP to produce argininosuccinate, which is converted to l-arginine and fumarate through argininosuccinate lyase (ArgH). We performed a biochemical analysis of Synechocystis 6803 ArgG (SyArgG) and obtained a Synechocystis 6803 mutant overexpressing SyArgG and ArgH of Synechocystis 6803 (SyArgH). The specific activity of SyArgG was lower than that of other arginine biosynthesis enzymes and SyArgG was inhibited by arginine, especially among amino acids and organic acids. Both arginine biosynthesis enzyme-overexpressing strains grew faster than the wild-type Synechocystis 6803. Based on previous reports and our results, we suggest that SyArgG is the rate-limiting enzyme in the arginine biosynthesis pathway in cyanobacteria and that arginine biosynthesis enzymes are similarly regulated by arginine in this cyanobacterium. Our results contribute to elucidating the regulation of arginine biosynthesis during nitrogen metabolism. << Less

  Plant Mol. Biol. 114:27-27(2024) [PubMed] [EuropePMC]

• Measurement of positional isotope exchange rates in enzyme-catalyzed reactions by fast atom bombardment mass spectrometry: application to argininosuccinate synthetase.

  Hilscher L.W., Hanson C.D., Russell D.H., Raushel F.M.

  Fast atom bombardment mass spectrometry (FAB-MS) has been used to measure positional isotope exchange rates in enzyme-catalyzed reactions. The technique has been applied to the reactions catalyzed by acetyl-CoA synthetase and argininosuccinate synthetase. The FAB technique is also able to quantita ... >> More

  Fast atom bombardment mass spectrometry (FAB-MS) has been used to measure positional isotope exchange rates in enzyme-catalyzed reactions. The technique has been applied to the reactions catalyzed by acetyl-CoA synthetase and argininosuccinate synthetase. The FAB technique is also able to quantitatively determine the oxygen-18 or oxygen-17 content of nucleotides on as little as 10 nmol of material with no prior derivatization. Acetyl-CoA synthetase has been shown by FAB-MS to catalyze the positional exchange of an oxygen-18 of ATP from the beta-nonbridge position to the alpha beta-bridge position in the presence of acetate. These results are consistent with acetyl adenylate as a reactive intermediate in this reaction. Argininosuccinate synthetase was shown not to catalyze a positional isotope exchange reaction designed to test for the formation of citrulline adenylate as a reactive intermediate. Argininosuccinate synthetase was also found not to catalyze the transfer of oxygen-18 from [ureido-18O]citrulline to the alpha-phosphorus of ATP in the absence of added aspartate. This experiment was designed to test for the transient formation of carbodiimide as a reactive intermediate. These results suggest that either argininosuccinate synthetase does not catalyze the formation of citrulline adenylate or the enzyme is able to completely suppress the rotation of the phosphoryl groups of PPi. << Less

  Biochemistry 24:5888-5893(1985) [PubMed] [EuropePMC]

• Characterization of human wild-type and mutant argininosuccinate synthetase proteins expressed in bacterial cells.

  Shaheen N., Kobayashi K., Terazono H., Fukushige T., Horiuchi M., Saheki T.

  Argininosuccinate synthetase (ASS) is a urea cycle enzyme with a tetrameric structure composed of identical subunits. Citrullinemia is an autosomal recessive disease caused by a deficiency of ASS. We have previously identified 20 mutations in ASS mRNA of human classical citrullinemia. However, it ... >> More

  Argininosuccinate synthetase (ASS) is a urea cycle enzyme with a tetrameric structure composed of identical subunits. Citrullinemia is an autosomal recessive disease caused by a deficiency of ASS. We have previously identified 20 mutations in ASS mRNA of human classical citrullinemia. However, it is difficult to evaluate the effects of each mutation on the enzyme structure and function, since most of the patients are compound heterozygotes. In the present study, wild-type ASS and 12 mutant ASSs were expressed with a bacterial expression system and analyzed enzymologically and immunochemically. The properties of the purified recombinant protein with wild-type human ASS showed good agreement with native enzyme purified from human liver. Mutant ASS proteins with an expected molecular mass, except for delta 7b/Ex16, were highly expressed in the bacterial cells. It was difficult to extract ASS proteins with some mutations (A118T, delta Ex7, R157H, R363W, R363L, G390R and ins37b/Ex15&16) from cells by freezing and thawing. Extractable mutant proteins were as follows: G280R mutant was extracted with an amount of ASS protein similar to wild-type but with no ASS activity, and A192V, R272C and R304W mutants detected various amounts of ASS protein (13, 110 and 33% of wild-type, respectively) with a low ASS activity and abnormal kinetics. Higher Km values for citrulline were obtained in mutant ASSs with A192V (15 mmol/1), R272C (4.2 mmol/l) and R304W. (190 mmol/l) than in wild-type ASS (0.056 mmol/l). The results confirm that these mutations are responsible for ASS deficiency and also indicate that these amino acid residues are important for the function and structure of ASS protein. << Less

  Enzyme Protein 48:251-264(1994) [PubMed] [EuropePMC]

• The 1.6 A crystal structure of E. coli argininosuccinate synthetase suggests a conformational change during catalysis.

  Lemke C.T., Howell P.L.

  <h4>Background</h4>Argininosuccinate synthetase (AS) is the rate-limiting enzyme of both the urea and arginine-citrulline cycles. In mammals, deficiency of AS leads to citrullinemia, a debilitating and often fatal autosomal recessive urea cycle disorder, whereas its overexpression for sustained ni ... >> More

  <h4>Background</h4>Argininosuccinate synthetase (AS) is the rate-limiting enzyme of both the urea and arginine-citrulline cycles. In mammals, deficiency of AS leads to citrullinemia, a debilitating and often fatal autosomal recessive urea cycle disorder, whereas its overexpression for sustained nitric oxide production via the arginine-citrulline cycle leads to the potentially fatal hypotension associated with septic and cytokine-induced circulatory shock.<h4>Results</h4>The crystal structure of E. coli AS (EAS) has been determined by the use of selenomethionine incorporation and MAD phasing. The structure has been refined at 1.6 A resolution in the absence of its substrates and at 2.0 A in the presence of aspartate and citrulline (EAS*CIT+ASP). Each monomer of this tetrameric protein has two structural domains: a nucleotide binding domain similar to that of the "N-type" ATP pyrophosphatase class of enzymes, and a novel catalytic/multimerization domain. The EAS*CIT+ASP structure clearly describes the binding of citrulline at the cleft between the two domains and of aspartate to a loop of the nucleotide binding domain, whereas homology modeling with the N-type ATP pyrophosphatases has provided the location of ATP binding.<h4>Conclusions</h4>The first three-dimensional structures of AS are reported. The fold of the nucleotide binding domain confirms AS as the fourth structurally defined member of the N-type ATP pyrophosphatases. The structures identify catalytically important residues and suggest the requirement for a conformational change during the catalytic cycle. Sequence similarity between the bacterial and human enzymes has been used for providing insight into the structural and functional effects of observed clinical mutations. << Less

  Structure 9:1153-1164(2001) [PubMed] [EuropePMC]

• Structure of human argininosuccinate synthetase.

  Karlberg T., Collins R., van den Berg S., Flores A., Hammarstrom M., Hogbom M., Holmberg Schiavone L., Uppenberg J.

  Argininosuccinate synthetase catalyzes the transformation of citrulline and aspartate into argininosuccinate and pyrophosphate using the hydrolysis of ATP to AMP and pyrophosphate. This enzymatic process constitutes the rate-limiting step in both the urea and arginine-citrulline cycles. Previous s ... >> More

  Argininosuccinate synthetase catalyzes the transformation of citrulline and aspartate into argininosuccinate and pyrophosphate using the hydrolysis of ATP to AMP and pyrophosphate. This enzymatic process constitutes the rate-limiting step in both the urea and arginine-citrulline cycles. Previous studies have investigated the crystal structures of argininosuccinate synthetase from bacterial species. In this work, the first crystal structure of human argininosuccinate synthetase in complex with the substrates citrulline and aspartate is presented. The human enzyme is compared with structures of argininosuccinate synthetase from bacteria. In addition, the structure also provides new insights into the function of the numerous clinical mutations identified in patients with type I citrullinaemia (also known as classic citrullinaemia). << Less

  Acta Crystallogr. D 64:279-286(2008) [PubMed] [EuropePMC]

• Almost all about citrulline in mammals.

  Curis E., Nicolis I., Moinard C., Osowska S., Zerrouk N., Benazeth S., Cynober L.

  Citrulline (Cit, C6H13N3O3), which is a ubiquitous amino acid in mammals, is strongly related to arginine. Citrulline metabolism in mammals is divided into two fields: free citrulline and citrullinated proteins. Free citrulline metabolism involves three key enzymes: NO synthase (NOS) and ornithine ... >> More

  Citrulline (Cit, C6H13N3O3), which is a ubiquitous amino acid in mammals, is strongly related to arginine. Citrulline metabolism in mammals is divided into two fields: free citrulline and citrullinated proteins. Free citrulline metabolism involves three key enzymes: NO synthase (NOS) and ornithine carbamoyltransferase (OCT) which produce citrulline, and argininosuccinate synthetase (ASS) that converts it into argininosuccinate. The tissue distribution of these enzymes distinguishes three "orthogonal" metabolic pathways for citrulline. Firstly, in the liver, citrulline is locally synthesized by OCT and metabolized by ASS for urea production. Secondly, in most of the tissues producing NO, citrulline is recycled into arginine via ASS to increase arginine availability for NO production. Thirdly, citrulline is synthesized in the gut from glutamine (with OCT), released into the blood and converted back into arginine in the kidneys (by ASS); in this pathway, circulating citrulline is in fact a masked form of arginine to avoid liver captation. Each of these pathways has related pathologies and, even more interestingly, citrulline could potentially be used to monitor or treat some of these pathologies. Citrulline has long been administered in the treatment of inherited urea cycle disorders, and recent studies suggest that citrulline may be used to control the production of NO. Recently, citrulline was demonstrated as a potentially useful marker of short bowel function in a wide range of pathologies. One of the most promising research directions deals with the administration of citrulline as a more efficient alternative to arginine, especially against underlying splanchnic sequestration of amino acids. Protein citrullination results from post-translational modification of arginine; that occurs mainly in keratinization-related proteins and myelins, and insufficiencies in this citrullination occur in some auto-immune diseases such as rheumatoid arthritis, psoriasis or multiple sclerosis. << Less

  Amino Acids 29:177-205(2005) [PubMed] [EuropePMC]

• Structures of argininosuccinate synthetase in enzyme-ATP substrates and enzyme-AMP product forms: stereochemistry of the catalytic reaction.

  Goto M., Omi R., Miyahara I., Sugahara M., Hirotsu K.

  Argininosuccinate synthetase reversibly catalyzes the ATP-dependent condensation of a citrulline with an aspartate to give argininosuccinate. The structures of the enzyme from Thermus thermophilus HB8 complexed with intact ATP and substrates (citrulline and aspartate) and with AMP and product (arg ... >> More

  Argininosuccinate synthetase reversibly catalyzes the ATP-dependent condensation of a citrulline with an aspartate to give argininosuccinate. The structures of the enzyme from Thermus thermophilus HB8 complexed with intact ATP and substrates (citrulline and aspartate) and with AMP and product (argininosuccinate) have been determined at 2.1- and 2.0-A resolution, respectively. The enzyme does not show the ATP-induced domain rotation observed in the enzyme from Escherichia coli. In the enzyme-substrate complex, the reaction sites of ATP and the bound substrates are adjacent and are sufficiently close for the reaction to proceed without the large conformational change at the domain level. The mobility of the triphosphate group in ATP and the side chain of citrulline play an important role in the catalytic action. The protonated amino group of the bound aspartate interacts with the alpha-phosphate of ATP and the ureido group of citrulline, thus stimulating the adenylation of citrulline. The enzyme-product complex explains how the citrullyl-AMP intermediate is bound to the active site. The stereochemistry of the catalysis of the enzyme is clarified on the basis of the structures of tAsS (argininosuccinate synthetase from T. thermophilus HB8) complexes. << Less

  J. Biol. Chem. 278:22964-22971(2003) [PubMed] [EuropePMC]