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Ornithine Transcarbamoylase
Ornithine transcarbamylase (OTC) (also called ornithine carbamoyltransferase) 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. Reaction mechanism Structure OTC is a trimeric protein. There are three active sites of the protein which are located at the cleft between the monomers. The carbamoyl phosphate binding domain resides on the N-terminal end of each monomer, while the C-terminal end contains the binding domain for ornithine. Both binding domains have a similar structural pattern with a central parall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. Almost all metabolic processes in the cell need enzyme catalysis in order to occur at rates fast enough to sustain life. Metabolic pathways depend upon enzymes to catalyze individual steps. The study of enzymes is called ''enzymology'' and the field of pseudoenzyme analysis recognizes that during evolution, some enzymes have lost the ability to carry out biological catalysis, which is often reflected in their amino acid sequences and unusual 'pseudocatalytic' properties. Enzymes are known to catalyze more than 5,000 biochemical reaction types. Other biocatalysts are catalytic RNA molecules, called ribozymes. Enzymes' specificity comes from their unique three-dimensional structures. Like all catalysts, enzymes increase the react ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uridine Monophosphate
Uridine monophosphate (UMP), also known as 5′-uridylic acid (conjugate base uridylate), is a nucleotide that is used as a monomer in RNA. It is an ester of phosphoric acid with the nucleoside uridine. UMP consists of the phosphate group, the pentose sugar ribose, and the nucleobase uracil; hence, it is a ribonucleotide monophosphate. As a substituent or radical its name takes the form of the prefix uridylyl-. The deoxy form is abbreviated dUMP. Covalent attachment of UMP (e.g. to a protein such as adenylyltransferase) is called uridylylation (or sometimes uridylation). Biosynthesis Uridine monophosphate is formed from Orotidine 5'-monophosphate (orotidylic acid) in a decarboxylation reaction catalyzed by the enzyme orotidylate decarboxylase. Uncatalyzed, the decarboxylation reaction is extremely slow (estimated to occur on average one time per 78 million years). Adequately catalyzed, the reaction takes place once per second, an increase of 1017-fold. In humans, the oro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biotin
Biotin (or vitamin B7) is one of the B vitamins. It is involved in a wide range of metabolic processes, both in humans and in other organisms, primarily related to the utilization of fats, carbohydrates, and amino acids. The name ''biotin'', borrowed from the German , derives from the Ancient Greek word (; 'life') and the suffix "-in" (a suffix used in chemistry usually to indicate 'forming'). Chemical description Biotin is classified as a heterocyclic compound, with a sulfur-containing ring fused ureido and tetrahydrothiophene group. A C5-carboxylic acid side chain is appended to one of the rings. The ureido ring, containing the −N−CO−N− group, serves as the carbon dioxide carrier in carboxylation reactions. Biotin is a coenzyme for five carboxylase enzymes, which are involved in the catabolism of amino acids and fatty acids, synthesis of fatty acids, and gluconeogenesis. Biotinylation of histone proteins in nuclear chromatin plays a role in chromatin stability an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hippurate
Hippuric acid ( Gr. ''hippos'', horse, ''ouron'', urine) is a carboxylic acid and organic compound. It is found in urine and is formed from the combination of benzoic acid and glycine. Levels of hippuric acid rise with the consumption of phenolic compounds (such as fruit juice, tea and wine). The phenols are first converted to benzoic acid, and then to hippuric acid and excreted in urine. Hippuric acid crystallizes in rhombic prisms which are readily soluble in hot water, melt at 187 °C, and decompose at about 240 °C. High concentrations of hippuric acid may also indicate a toluene intoxication; however, scientists have called this correlation into question because there are other variables that affect levels of hippuric acid. When many aromatic compounds such as benzoic acid and toluene are taken internally, they are converted to hippuric acid by reaction with the amino acid, glycine. Synthesis A modern synthesis of hippuric acid involves the acylation of glycin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glycine
Glycine (symbol Gly or G; ) is an amino acid that has a single hydrogen atom as its side chain. It is the simplest stable amino acid ( carbamic acid is unstable), with the chemical formula NH2‐ CH2‐ COOH. Glycine is one of the proteinogenic amino acids. It is encoded by all the codons starting with GG (GGU, GGC, GGA, GGG). Glycine is integral to the formation of alpha-helices in secondary protein structure due to its compact form. For the same reason, it is the most abundant amino acid in collagen triple-helices. Glycine is also an inhibitory neurotransmitter – interference with its release within the spinal cord (such as during a ''Clostridium tetani'' infection) can cause spastic paralysis due to uninhibited muscle contraction. It is the only achiral proteinogenic amino acid. It can fit into hydrophilic or hydrophobic environments, due to its minimal side chain of only one hydrogen atom. History and etymology Glycine was discovered in 1820 by the French chemist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Benzoate
Sodium benzoate is the sodium salt of benzoic acid, widely used as a food preservative (with an E number of E211) and a pickling agent. It appears as a white crystalline chemical with the formula C6H5COONa. Production Sodium benzoate is commonly produced by the neutralization of sodium hydroxide (NaOH) with benzoic acid (C6H5COOH), which is itself produced commercially by partial oxidation of toluene with oxygen. Natural occurrence Many foods are natural sources of benzoic acid, its salts, and its esters. Fruits and vegetables can be rich sources, particularly berries such as cranberry and bilberry. Other sources include seafood, such as prawns, and dairy products. Uses As a preservative Sodium benzoate can act as a food preservative. It is most widely used in acidic foods such as salad dressings (for example acetic acid in vinegar), carbonated drinks ( carbonic acid), jams and fruit juices (citric acid), pickles (acetic acid), condiments, and frozen yogurt toppings. It ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cerebral Edema
Cerebral edema is excess accumulation of fluid ( edema) in the intracellular or extracellular spaces of the brain. This typically causes impaired nerve function, increased pressure within the skull, and can eventually lead to direct compression of brain tissue and blood vessels. Symptoms vary based on the location and extent of edema and generally include headaches, nausea, vomiting, seizures, drowsiness, visual disturbances, dizziness, and in severe cases, coma and death. Cerebral edema is commonly seen in a variety of brain injuries including ischemic stroke, subarachnoid hemorrhage, traumatic brain injury, subdural, epidural, or intracerebral hematoma, hydrocephalus, brain cancer, brain infections, low blood sodium levels, high altitude, and acute liver failure. Diagnosis is based on symptoms and physical examination findings and confirmed by serial neuroimaging ( computed tomography scans and magnetic resonance imaging). The treatment of cerebral edema depends ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coma
A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhibit a complete absence of wakefulness and are unable to consciously feel, speak or move. Comas can be derived by natural causes, or can be medically induced. Clinically, a coma can be defined as the inability consistently to follow a one-step command. It can also be defined as a score of ≤ 8 on the Glasgow Coma Scale (GCS) lasting ≥ 6 hours. For a patient to maintain consciousness, the components of ''wakefulness'' and ''awareness'' must be maintained. Wakefulness describes the quantitative degree of consciousness, whereas awareness relates to the qualitative aspects of the functions mediated by the cortex, including cognitive abilities such as attention, sensory perception, explicit memory, language, the execution of tasks, temporal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lethargy
Lethargy is a state of tiredness, sleepiness, weariness, fatigue, sluggishness or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to inadequate sleep, overexertion, overworking, stress, lack of exercise, improper nutrition, boredom, or a symptom of an underlying illness or a disorder. It may also be a side-effect of medication or caused by an interaction between medications or medication(s) and alcohol. It may also be an altered level of consciousness. When part of a normal response, lethargy often resolves with rest, adequate sleep, decreased stress, physical exercise, and good nutrition. Lethargy's symptoms however can last days or even months, so it can be a sign of a recent underlying illness or infection if it doesn't resolve normally. See also * Clinical depression Major depressive disorder (MDD), also known as clinical depression, is a mental disorder characterized by at least two wee ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Somnolence
Somnolence (alternatively sleepiness or drowsiness) is a state of strong desire for sleep, or sleeping for unusually long periods (compare hypersomnia). It has distinct meanings and causes. It can refer to the usual state preceding falling asleep, the condition of being in a drowsy state due to circadian rhythm disorders, or a symptom of other health problems. It can be accompanied by lethargy, weakness and lack of mental agility. Somnolence is often viewed as a symptom rather than a disorder by itself. However, the concept of somnolence recurring at certain times for certain reasons constitutes various disorders, such as excessive daytime sleepiness, shift work sleep disorder, and others; and there are medical codes for somnolence as viewed as a disorder. Sleepiness can be dangerous when performing tasks that require constant concentration, such as driving a vehicle. When a person is sufficiently fatigued, microsleeps may be experienced. In individuals deprived of sleep, som ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hyperammonemia
Hyperammonemia 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. Ammonia is a substance that contains nitrogen. It is a product of the catabolism of protein. It is converted to the less toxic substance urea prior to excretion in urine by the kidneys. The metabolic pathways that synthesize urea involve reactions that start in the mitochondria and then move into the cytosol. The process is known as the urea cycle, which comprises several enzymes acting in sequence. It is greatly exacerbated by common zinc deficiency, which raises ammonia levels further. Signs and symptoms Complication Hyperammonemia is one of the metabolic derangements that contribute to hepatic encephalopathy, which can cause swelling of astrocytes and stimulation of NMDA receptors in the brain. Overstimulation of NMDA receptors induces excitotoxicity. Diagnosis Types Primary vs. s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Primary Care Physician
A primary care physician (PCP) is a physician who provides both the first contact for a person with an undiagnosed health concern as well as continuing care of varied medical conditions, not limited by cause, organ system, or diagnosis. The term is primarily used in the United States. In the past, the equivalent term was 'general practitioner' in the US; however in the United Kingdom and other countries the term general practitioner is still used. A core element in general practice is continuity that bridges episodes of various illnesses. Greater continuity with a general practitioner has been shown to reduce the need for out-of-hours services and acute hospital admittance. Furthermore, continuity by a general practitioner reduces mortality. All physicians first complete medical school ( MD, MBBS, or DO). To become primary care physicians, medical school graduates then undertake postgraduate training in primary care programs, such as family medicine (also called family prac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
