Nucleotides are organic molecules composed of a nitrogenous base, a pentose sugar and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecules within all life-forms on Earth. Nucleotides are obtained in the diet and are also synthesized from common nutrients by the liver.
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 is a non-proteinogenic α-amino acid that plays a role in the urea cycle. Ornithine is abnormally accumulated in the body in ornithine transcarbamylase deficiency. The radical is ornithyl.
The organic compound citrulline is an α-amino acid. Its name is derived from citrullus, the Latin word for watermelon. Although named and described by gastroenterologists since the late 19th century, it was first isolated from watermelon in 1914 by Japanese researchers Yatarō Koga (古賀彌太郎) and Ryō Ōtake (大嶽了) and further codified by Mitsunori Wada of Tokyo Imperial University in 1930. It has the formula H2NC(O)NH(CH2)3CH(NH2)CO2H. It is a key intermediate in the urea cycle, the pathway by which mammals excrete ammonia by converting it into urea. Citrulline is also produced as a byproduct of the enzymatic production of nitric oxide from the amino acid arginine, catalyzed by nitric oxide synthase.
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.
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.
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.
Argininosuccinate synthase or synthetase is an enzyme that catalyzes the synthesis of argininosuccinate from citrulline and aspartate. In humans, argininosuccinate synthase is encoded by the ASS gene located on chromosome 9.
Cyanophycin, also known as CGP or multi-L-arginyl-poly, is a non-protein, non-ribosomally produced amino acid polymer composed of an aspartic acid backbone and arginine side groups.
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.
Pyrimidine biosynthesis occurs both in the body and through organic synthesis.
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.
Carbamoyl phosphate synthetase (glutamine-hydrolysing) is an enzyme that catalyzes the reactions that produce carbamoyl phosphate in the cytosol. Its systemic name is hydrogen-carbonate:L-glutamine amido-ligase .
In enzymology, a N-acetylornithine carbamoyltransferase (EC 2.1.3.9) is an enzyme that catalyzes the chemical reaction
l-Canaline ) is a non-proteinogenic amino acid. The compound is found in legumes that contain canavanine, from which it is produced by the action of arginase. The most common-used source for this amino acid is the jack bean, Canavalia ensiformis.
In molecular biology, the ATCase/OTCase family is a protein family which contains two related enzymes: aspartate carbamoyltransferase EC 2.1.3.2 and ornithine carbamoyltransferase EC 2.1.3.3. It has been shown that these enzymes are evolutionary related. The predicted secondary structure of both enzymes is similar and there are some regions of sequence similarities. One of these regions includes three residues which have been shown, by crystallographic studies to be implicated in binding the phosphoryl group of carbamoyl phosphate and may also play a role in trimerisation of the molecules. The N-terminal domain is the carbamoyl phosphate binding domain. The C-terminal domain is an aspartate/ornithine-binding domain.
Arginine and proline metabolism is one of the central pathways for the biosynthesis of the amino acids arginine and proline from glutamate. The pathways linking arginine, glutamate, and proline are bidirectional. Thus, the net utilization or production of these amino acids is highly dependent on cell type and developmental stage. Altered proline metabolism has been linked to metastasis formation in breast cancer.
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.
Carbamoyl phosphate synthetase III is one of the three isoforms of the carbamoyl phosphate synthetase, an enzyme that catalyzes the active production of carbamoyl phosphate in many organisms.
