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Phosphoglycerate Dehydrogenase
Phosphoglycerate dehydrogenase (PHGDH) is an enzyme that catalyzes the chemical reactions :3-phospho-D-glycerate + NAD+ \rightleftharpoons 3-phosphonooxypyruvate + NADH + H+ :2-hydroxyglutarate + NAD+ \rightleftharpoons 2-oxoglutarate + NADH + H+ The two substrates of this enzyme are 3-phospho-D-glycerate and NAD+, whereas its 3 products are 3-phosphohydroxypyruvate, NADH, and H+ It is also possible that two substrates of this enzyme are 2-hydroxyglutarate and NAD+, whereas its 3 products are 2-oxoglutarate, NADH, and H+. As of 2012, the most widely studied variants of PHGDH are from the '' E. coli'' and '' M. tuberculosis'' genomes. In humans, this enzyme is encoded by the ''PHGDH'' gene. Function 3-Phosphoglycerate dehydrogenase catalyzes the transition of 3-phosphoglycerate into 3-phosphohydroxypyruvate, which is the committed step in the phosphorylated pathway of L-serine biosynthesis. It is also essential in cysteine and glycine synthesis, which lie further down ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydride
In chemistry, a hydride is formally the anion of hydrogen( H−). The term is applied loosely. At one extreme, all compounds containing covalently bound H atoms are called hydrides: water (H2O) is a hydride of oxygen, ammonia is a hydride of nitrogen, etc. For inorganic chemists, hydrides refer to compounds and ions in which hydrogen is covalently attached to a less electronegative element. In such cases, the H centre has nucleophilic character, which contrasts with the protic character of acids. The hydride anion is very rarely observed. Almost all of the elements form binary compounds with hydrogen, the exceptions being He, Ne, Ar, Kr, Pm, Os, Ir, Rn, Fr, and Ra. Exotic molecules such as positronium hydride have also been made. Bonds Bonds between hydrogen and the other elements range from highly to somewhat covalent. Some hydrides, e.g. boron hydrides, do not conform to classical electron-counting rules and the bonding is described in terms of multi-centered ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microcephaly
Microcephaly (from New Latin ''microcephalia'', from Ancient Greek μικρός ''mikrós'' "small" and κεφαλή ''kephalé'' "head") is a medical condition involving a smaller-than-normal head. Microcephaly may be present at birth or it may develop in the first few years of life. Since brain growth is correlated with head growth, people with this disorder often have an intellectual disability, poor motor function, poor speech, abnormal facial features, seizures and dwarfism. The disorder is caused by a disruption to the genetic processes that form the brain early in pregnancy, though the cause is not identified in most cases. Many genetic syndromes can result in microcephaly, including chromosomal and single-gene conditions, though almost always in combination with other symptoms. Mutations that result solely in microcephaly (primary microcephaly) exist but are less common. External toxins to the embryo, such as alcohol during pregnancy or vertically transmitted infec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
D-glycerate Dehydrogenase Deficiency
D-glycerate dehydrogenase deficiency (or 3-phosphoglycerate dehydrogenase deficiency, PHGDH deficiency, PHGDHD) is a rare autosomal metabolic disease where the young patient is unable to produce an enzyme necessary to convert 3-phosphoglycerate into 3-phosphohydroxypyruvate, which is the only way for humans to synthesize serine.This disorder is called Neu–Laxova syndrome in neonates. Symptoms and signs In addition significantly shortening lifespan, PHGDH deficiencies are known to cause congenital microcephaly, psychomotor retardation, and seizures in both humans and rats, presumably due to the essential signaling within the nervous system that serine, glycine, and other downstream molecules are intimately involved with. Cause Homozygous or compound heterozygous mutations in 3-phosphoglycerate dehydrogenase (PHGDH) cause Neu-Laxova syndrome and phosphoglycerate dehydrogenase deficiency. Mechanism 3-Phosphoglycerate dehydrogenase catalyzes the transition of 3-phosphoglyc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neu–Laxova Syndrome
Neu–Laxova syndrome (NLS, also known as Neu syndrome; Neu-Povysilová syndrome; or 3-phosphoglycerate dehydrogenase deficiency, neonate form) is a rare autosomal recessive disorder characterized by severe intrauterine growth restriction and multiple congenital malformations. Neu–Laxova syndrome is a very severe disorder, leading to stillbirth or death shortly after birth. It was first described by Dr. Richard Neu in 1971 and Dr. Renata Laxova in 1972 as a lethal disorder in siblings with multiple malformations. Neu–Laxova syndrome is an extremely rare disorder with less than 100 cases reported in medical literature. Signs and symptoms Neu-Laxova syndrome presents with severe malformations leading to prenatal or neonatal death. Typically, NLS involves characteristic facial features, decreased fetal movements and skin abnormalities. Fetuses or newborns with Neu–Laxova syndrome have typical facial characteristics which include proptosis (bulging eyes) with eyelid malformati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Compound Heterozygosity
In medical genetics, compound heterozygosity is the condition of having two or more heterogeneous recessive alleles at a particular locus that can cause genetic disease in a heterozygous state; that is, an organism is a compound heterozygote when it has two recessive alleles for the same gene, but with those two alleles being different from each other (for example, both alleles might be mutated but at different locations). Compound heterozygosity reflects the diversity of the mutation base for many autosomal recessive genetic disorders; mutations in most disease-causing genes have arisen many times. This means that many cases of disease arise in individuals who have two unrelated alleles, who technically are heterozygotes, but both the alleles are defective. These disorders are often best known in some classic form, such as the homozygous recessive case of a particular mutation that is widespread in some population. In its compound heterozygous forms, the disease may have lower penet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lysine
Lysine (symbol Lys or K) is an α-amino acid that is a precursor to many proteins. It contains an α-amino group (which is in the protonated form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO− form under biological conditions), and a side chain lysyl ((CH2)4NH2), classifying it as a basic, charged (at physiological pH), aliphatic amino acid. It is encoded by the codons AAA and AAG. Like almost all other amino acids, the α-carbon is chiral and lysine may refer to either enantiomer or a racemic mixture of both. For the purpose of this article, lysine will refer to the biologically active enantiomer L-lysine, where the α-carbon is in the ''S'' configuration. The human body cannot synthesize lysine. It is essential in humans and must therefore be obtained from the diet. In organisms that synthesise lysine, two main biosynthetic pathways exist, the diaminopimelate and α-aminoadipate pathways, which employ distinct e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Histidine
Histidine (symbol His or H) is an essential amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated –NH3+ form under biological conditions), a carboxylic acid group (which is in the deprotonated –COO− form under biological conditions), and an imidazole side chain (which is partially protonated), classifying it as a positively charged amino acid at physiological pH. Initially thought essential only for infants, it has now been shown in longer-term studies to be essential for adults also. It is encoded by the codons CAU and CAC. Histidine was first isolated by Albrecht Kossel and Sven Gustaf Hedin in 1896. It is also a precursor to histamine, a vital inflammatory agent in immune responses. The acyl radical is histidyl. Properties of the imidazole side chain The conjugate acid (protonated form) of the imidazole side chain in histidine has a p''K''a of approximately 6.0. Thus, below a pH of 6, the imidazole ring ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetramer
A tetramer () (''tetra-'', "four" + '' -mer'', "parts") is an oligomer formed from four monomers or subunits. The associated property is called ''tetramery''. An example from inorganic chemistry is titanium methoxide with the empirical formula Ti(OCH3)4, which is tetrameric in solid state and has the molecular formula Ti4(OCH3)16. An example from organic chemistry is kobophenol A, a substance that is formed by combining four molecules of resveratrol. In biochemistry, it similarly refers to a biomolecule formed of four units, that are the same (homotetramer), i.e. as in Concanavalin A or different (heterotetramer), i.e. as in hemoglobin. Hemoglobin has 4 similar sub-units while immunoglobulins have 2 very different sub-units. The different sub-units may have each their own activity, such as binding biotin in avidin tetramers, or have a common biological property, such as the allosteric binding of oxygen in hemoglobin. See also * Cluster chemistry; atomic and molecular clusters ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cooperativity
Cooperativity is a phenomenon displayed by systems involving identical or near-identical elements, which act dependently of each other, relative to a hypothetical standard non-interacting system in which the individual elements are acting independently. One manifestation of this is enzymes or receptors that have multiple binding sites where the affinity of the binding sites for a ligand is ''apparently'' increased, positive cooperativity, or decreased, negative cooperativity, upon the binding of a ligand to a binding site. For example, when an oxygen atom binds to one of hemoglobin's four binding sites, the affinity to oxygen of the three remaining available binding sites increases; i.e. oxygen is more likely to bind to a hemoglobin bound to one oxygen than to an unbound hemoglobin. This is referred to as cooperative binding. We also see cooperativity in large chain molecules made of many identical (or nearly identical) subunits (such as DNA, proteins, and phospholipids), when su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glycolysis
Glycolysis is the metabolic pathway that converts glucose () into pyruvate (). The free energy released in this process is used to form the high-energy molecules adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide (NADH). Glycolysis is a sequence of ten reactions catalyzed by enzymes. Glycolysis is a metabolic pathway that does not require oxygen (In anaerobic conditions pyruvate is converted to lactic acid). The wide occurrence of glycolysis in other species indicates that it is an ancient metabolic pathway. Indeed, the reactions that make up glycolysis and its parallel pathway, the pentose phosphate pathway, occur in the oxygen-free conditions of the Archean oceans, also in the absence of enzymes, catalyzed by metal. In most organisms, glycolysis occurs in the liquid part of cells, the cytosol. The most common type of glycolysis is the ''Embden–Meyerhof–Parnas (EMP) pathway'', which was discovered by Gustav Embden, Otto Meyerhof, and Jakub Karol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
