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| N-Acetylglutamate synthase deficiency | |
|---|---|
| Other names | Synthetase deficiency |
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| N-Acetylglutamic acid | |
| Specialty | Medical genetics |
N-Acetylglutamate synthase deficiency is an autosomal recessive urea cycle disorder.
The symptoms are visible within the first week of life and if not detected and diagnosed correctly immediately consequences are fatal.
The chromosome found to be carrying the gene encoding for N-acetyl glutamate synthase is chromosome 17q (q stands for longer arm of the chromosome) in humans and chromosome 11 in mice. In both organisms, the chromosome consists of seven exons and six introns and non-coding sequence.
The cause for this disorder is a single base deletion that led to frameshift mutation, and thus the error in gene's coding for this specific enzyme.
Carbamoyl phosphate synthase I is an enzyme found in mitochondrial matrix and it catalyzes the very first reaction of the urea cycle, in which carbamoyl phosphate is produced.
Carbamoyl phosphate synthase 1, abbreviated as CPS1, is activated by its natural activator N-acetyl glutamate, which in turn is synthesized from acetyl-CoA and glutamic acid in the reaction catalyzed by N-acetyl glutamate synthase, commonly called NAGS. N-acetyl glutamate is required for the urea cycle to take place.
Deficiency in N-acetylglutamate synthase or a genetic mutation in the gene coding for the enzyme will lead to urea cycle failure in which ammonia is not converted to urea, but rather accumulated in blood leading to the condition called type I hyperammonemia. This is a severe neonatal disorder with fatal consequences, if not detected immediately upon birth.
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Although there is currently no cure, treatment includes injections of structurally similar compound, carglumic acid, an analogue of N-acetyl glutamate. This analogue likewise activates CPS1. This treatment mitigates the intensity of the disorder.
If symptoms are detected early enough and the patient is injected with this compound, levels of severe mental retardation can be slightly lessened, but brain damage is irreversible.
Also: hemodialysis for emergent hyperammonemic crisis, Na benzoate, Na phenylacetate, Na phenylbutyrate, low-protein diet supplemented with essential amino acid mixture and arginine, citrulline, experimental attempts at gene therapy, liver transplantation (which is curative), and also N-carbamylglutamate supplementation.
The urea cycle (also known as the ornithine cycle) is a cycle of biochemical reactions that produces urea (NH2)2CO from ammonia (NH3). Animals that use this cycle, mainly amphibians and mammals, are called ureotelic.
Ornithine transcarbamylase (OTC) is an enzyme that catalyzes the reaction between carbamoyl phosphate (CP) and ornithine (Orn) to form citrulline (Cit) and phosphate (Pi). There are two classes of OTC: anabolic and catabolic. This article focuses on anabolic OTC. Anabolic OTC facilitates the sixth step in the biosynthesis of the amino acid arginine in prokaryotes. In contrast, mammalian OTC plays an essential role in the urea cycle, the purpose of which is to capture toxic ammonia and transform it into urea, a less toxic nitrogen source, for excretion.
Carbamoyl phosphate is an anion of biochemical significance. In land-dwelling animals, it is an intermediary metabolite in nitrogen disposal through the urea cycle and the synthesis of pyrimidines. Its enzymatic counterpart, carbamoyl phosphate synthetase I, interacts with a class of molecules called sirtuins, NAD dependent protein deacetylases, and ATP to form carbamoyl phosphate. CP then enters the urea cycle in which it reacts with ornithine to form citrulline.
In biochemistry, a transferase is any one of a class of enzymes that catalyse the transfer of specific functional groups from one molecule to another. They are involved in hundreds of different biochemical pathways throughout biology, and are integral to some of life's most important processes.
Propionic acidemia, also known as propionic aciduria or propionyl-CoA carboxylase deficiency, is a rare autosomal recessive metabolic disorder, classified as a branched-chain organic acidemia.
Hyperammonemia, or high ammonia levels, is a metabolic disturbance characterised by an excess of ammonia in the blood. It is a dangerous condition that may lead to brain injury and death. It may be primary or secondary.
Ornithine transcarbamylase deficiency also known as OTC deficiency is the most common urea cycle disorder in humans. Ornithine transcarbamylase, the defective enzyme in this disorder, is the final enzyme in the proximal portion of the urea cycle, responsible for converting carbamoyl phosphate and ornithine into citrulline. OTC deficiency is inherited in an X-linked recessive manner, meaning males are more commonly affected than females.
Biosynthesis, i.e., chemical synthesis occurring in biological contexts, is a term most often referring to multi-step, enzyme-catalyzed processes where chemical substances absorbed as nutrients serve as enzyme substrates, with conversion by the living organism either into simpler or more complex products. Examples of biosynthetic pathways include those for the production of amino acids, lipid membrane components, and nucleotides, but also for the production of all classes of biological macromolecules, and of acetyl-coenzyme A, adenosine triphosphate, nicotinamide adenine dinucleotide and other key intermediate and transactional molecules needed for metabolism. Thus, in biosynthesis, any of an array of compounds, from simple to complex, are converted into other compounds, and so it includes both the catabolism and anabolism of complex molecules. Biosynthetic processes are often represented via charts of metabolic pathways. A particular biosynthetic pathway may be located within a single cellular organelle, while others involve enzymes that are located across an array of cellular organelles and structures.
In the mitochondrion, the matrix is the space within the inner membrane. The word "matrix" stems from the fact that this space is viscous, compared to the relatively aqueous cytoplasm. The mitochondrial matrix contains the mitochondrial DNA, ribosomes, soluble enzymes, small organic molecules, nucleotide cofactors, and inorganic ions.[1] The enzymes in the matrix facilitate reactions responsible for the production of ATP, such as the citric acid cycle, oxidative phosphorylation, oxidation of pyruvate, and the beta oxidation of fatty acids.
N-Acetylglutamic acid (also referred to as N-acetylglutamate, abbreviated NAG, chemical formula C7H11NO5) is biosynthesized from glutamate and acetylornithine by ornithine acetyltransferase, and from glutamic acid and acetyl-CoA by the enzyme N-acetylglutamate synthase. The reverse reaction, hydrolysis of the acetyl group, is catalyzed by a specific hydrolase. It is the first intermediate involved in the biosynthesis of arginine in prokaryotes and simple eukaryotes and a regulator in the process known as the urea cycle that converts toxic ammonia to urea for excretion from the body in vertebrates.
The enzyme argininosuccinate lyase (EC 4.3.2.1, ASL, argininosuccinase; systematic name 2-(N ω-L-arginino)succinate arginine-lyase (fumarate-forming)) catalyzes the reversible breakdown of argininosuccinate:
Methylmalonyl-CoA mutase is a mitochondrial homodimer apoenzyme that focuses on the catalysis of methylmalonyl CoA to succinyl CoA. The enzyme is bound to adenosylcobalamin, a hormonal derivative of vitamin B12 in order to function. Methylmalonyl-CoA mutase deficiency is caused by genetic defect in the MUT gene responsible for encoding the enzyme. Deficiency in this enzyme accounts for 60% of the cases of methylmalonic acidemia.
N-Acetylglutamate synthase (NAGS) is an enzyme that catalyses the production of N-acetylglutamate (NAG) from glutamate and acetyl-CoA.
Carbamoyl phosphate synthetase I is a ligase enzyme located in the mitochondria involved in the production of urea. Carbamoyl phosphate synthetase I transfers an ammonia molecule to a molecule of bicarbonate that has been phosphorylated by a molecule of ATP. The resulting carbamate is then phosphorylated with another molecule of ATP. The resulting molecule of carbamoyl phosphate leaves the enzyme.
Carbamoyl phosphate synthetase I deficiency is an autosomal recessive metabolic disorder that causes ammonia to accumulate in the blood due to a lack of the enzyme carbamoyl phosphate synthetase I. Ammonia, which is formed when proteins are broken down in the body, is toxic if the levels become too high. The nervous system is especially sensitive to the effects of excess ammonia.
Ornithine translocase deficiency, also called hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome, is a rare autosomal recessive urea cycle disorder affecting the enzyme ornithine translocase, which causes ammonia to accumulate in the blood, a condition called hyperammonemia.
Carbamoyl phosphate synthetase catalyzes the ATP-dependent synthesis of carbamoyl phosphate from glutamine or ammonia and bicarbonate. This ATP-grasp enzyme catalyzes the reaction of ATP and bicarbonate to produce carboxy phosphate and ADP. Carboxy phosphate reacts with ammonia to give carbamic acid. In turn, carbamic acid reacts with a second ATP to give carbamoyl phosphate plus ADP.
In enzymology, an aminoacylase (EC 3.5.1.14) is an enzyme that catalyzes the chemical reaction
Ornithine aminotransferase deficiency is an inborn error of ornithine metabolism, caused by decreased activity of the enzyme ornithine aminotransferase. Biochemically, it can be detected by elevated levels of ornithine in the blood. Clinically, it presents initially with poor night vision, which slowly progresses to total blindness. It is believed to be inherited in an autosomal recessive manner. Approximately 200 known cases have been reported in the literature. The incidence is highest in Finland, estimated at 1:50,000.
Citrullinemia type I (CTLN1), also known as arginosuccinate synthetase deficiency, is a rare disease caused by a deficiency in argininosuccinate synthetase, an enzyme involved in excreting excess nitrogen from the body. There are mild and severe forms of the disease, which is one of the urea cycle disorders.