|Medical Dictionary - Dictionary of Medicine and Human Biology|
A phosphagen; a compound of creatine (through its NH2 group) with phosphoric acid; a source of energy in the contraction of vertebrate muscle, its breakdown furnishing phosphate for the resynthesis of ATP from ADP by creatine kinase. Cf.:phosphoarginine. SYN: creatine phosphate, Nω-phosphonocreatine.
A diesterified orthophosphoric acid, RO–(PO2H)–OR′, as in the nucleic acids. p. hydrolases SYN: phosphodiesterases.
Enzymes (EC 3.1.4.x) cleaving phosphodiester bonds, such as those in cAMP or between nucleotides in nucleic acids, liberating smaller poly- or oligonucleotide units or mononucleotides but not orthophosphate. SYN: phosphodiester hydrolases. spleen p. SYN: micrococcal endonuclease.
SYN: phosphop.pyruvic acid carboxykinase.
phosphoenolpyruvic acid (fos′fo-e′nol-pi-roo′vik)
The phosphoric ester of pyruvic acid in the latter's p. form; an intermediate in the conversion of d-glucose to pyruvic acid and an example of a high-energy phosphate ester. phosphop.pyruvic acid carboxykinase an enzyme that catalyzes the reaction of oxaloacetate and GTP to form phosphoenolpyruvic acid, CO2, and GDP; a key enzyme in gluconeogenesis; the biosynthesis of this enzyme is decreased by insulin. SYN: phosphop.pyruvate carboxykinase.
A key intermediate in the formation of cephalins; formed in liver and brain by phosphorylation of ethanolamine. p. cytidylyltransferase a key enzyme in the biosynthesis of cephalins; it catalyzes the reaction of p. and CTP to form CDP-ethanolamine and pyrophosphate.
SYN: fructose-bisphosphate aldolase.
Fructose-1-phosphate kinase;an enzyme catalyzing phosphorylation of d-fructose 1-phosphate by ATP (or other NTP) to d-fructose 1,6-bisphosphate and ADP (or other NDP); a key step in the metabolism of d-fructose; a deficiency of the muscle enzyme can result in glycogen storage disease type VII.
Phosphofructokinase I;an enzyme that catalyzes the phosphorylation of d-fructose 6-phosphate by ATP (or other NTP) to fructose 1,6-bisphosphate and ADP (or other NDP); this enzyme catalyzes a step in glycolysis; it is inhibited by elevated levels of either ATP or citrate; a deficiency of this enzyme can lead to hemolytic anemia. SYN: phosphohexokinase.
SYN: UDPglucose-hexose-1-phosphate uridylyltransferase.
An enzyme that, in the presence of ATP, catalyzes the phosphorylation of d-glucose 1-phosphate to form d-glucose 1,6-bisphosphate and ADP; found in yeast and muscle; d-glucose 1,6-bisphosphate is a required cofactor of one of the enzymes in glycogenolysis. SYN: glucose-1-phosphate kinase.
An enzyme that catalyzes the reversible reaction, α-d-glucose 1-phosphate &rrl; α-d-glucose 6-phosphate, with glucose 1,6-bisphosphate a necessary cofactor; one of the steps in glycogenolysis. SYN: glucose phosphomutase.
phosphogluconate dehydrogenase (fos-fo-gloo′ko-nat)
6-phosphogluconic dehydrogenase;an enzyme catalyzing the reaction of 6-phospho-d-gluconate and NAD(P)+ to form 6-phospho-2-keto-d-gluconate and NAD(P)H; a deficiency of this enzyme has been reported, but no cell disruption has been observed.
phosphogluconate dehydrogenase (decarboxylating)
An enzyme, which is part of the pentose phosphate shunt, that catalyzes the reaction of 6-phospho-d-gluconate and NADP+ to produce CO2, NADPH, and d-ribulose 5-phosphate.
A hydrolase that catalyzes the hydrolysis of 6-phospho-d-glucono δ-lactone to 6-phospho-d-gluconate; this enzyme is a part of the pentose phosphate shunt.
An intermediate in the pentose phosphate pathway that is synthesized from d-glucose 6-phosphate.
phosphoglycerate kinase (fos-fo-glis′er-at)
An enzyme catalyzing the formation of 3-phospho-d-glyceroyl phosphate and ADP from 3-phospho-d-glycerate and ATP; this enzyme is a part of the glycolytic pathway; a deficiency of p. (an X-linked disorder) results in impaired glycolysis in most cells.
phosphoglyceric acid (fos′fo-gli-ser′ik, -glis′er-ik)
1. Glyceroyl phosphoric acid; glyceroyl phosphate;an acid anhydride between glyceric acid and phosphoric acid. 2. 2-P.;the deprotonated form, 2-phosphoglycerate, is an intermediate in glycolysis. 3. 3-P.;the deprotonated form, 3-phosphoglycerate, is an intermediate in glycolysis.
Acylglycerol and diacylglycerol phosphates;constituents of nerve tissue, and involved in fat transport and storage.
An isomerizing enzyme catalyzing the reversible interconversion of 2-phosphoglycerate and 3-phosphoglycerate with 2,3-bisphosphoglycerate present as a cofactor; a deficiency of this enzyme, which plays a role in glycolysis, is an inherited disorder that results in an intolerance for strenuous exercise.
SYN: glucose-phosphate isomerase.
phosphohexose isomerase (fos-fo-hek′sos)
SYN: glucose-phosphate isomerase.
Phosphoric monoester hydrolases;enzymes (EC 3.1.3.x) cleaving phosphoric acid (as orthophosphate) from its esters; trivial names usually end in phosphate.
A phosphotransferase or a kinase.
An enzyme that catalyzes the hydrolysis of a phospholipid. SYN: lecithinase. p. A1 an enzyme that hydrolyzes a lecithin (1,2-diacylglycerophosphocholine) to a 2-acylglycerophosphocholine and a fatty acid anion. p. A2 an enzyme that catalyzes the hydrolysis of a lecithin to a lysolecithin by removing the 2-acyl group; also acts on other phospholipids by removing a fatty acid from the 2-position; this enzyme has an important role in prostaglandin and leukotriene biosynthesis. SYN: lecithinase A, phosphatidase, phosphatidolipase. p. B 1. SYN: lysophospholipase. 2. a mixture of p. A1 and p. A2. p. C Clostridium welchii α-toxin; Clostridium oedematiens β- and γ-toxins;an enzyme that catalyzes the hydrolysis of phosphatidylcholine (and perhaps other phospholipids) to produce choline phosphate and 1,2-diacylglycerol; also acts on sphingomyelin; a key enzyme in the formation of inositol 1,4,5-trisphosphate. SYN: lecithinase C, lipophosphodiesterase I. p. D an enzyme that hydrolyzes phosphatidylcholine to produce choline and a phosphatidate; also acts on other phosphatidyl esters. SYN: choline phosphatase, lecithinase D, lipophosphodiesterase II.
A lipid containing phosphorus, thus including the lecithins and other phosphatidyl derivatives, sphingomyelin, and plasmalogens; the basic constituents of biomembranes.
One of a number of enzymes (mutases) (EC 5.4.2.x) that apparently catalyze intramolecular transfer because the donor is regenerated ( e.g., phosphoglyceromutase, phosphoglucomutase). SYN: phosphodismutase.
Necrosis of the bone of the jaw, a result of poisoning by inhalation of phosphorus fumes, occurring especially in persons who work with the element. [phosphorus + G. nekrosis, death (necrosis)]
The radical, (PR4)+.
The prosthetic group of the acyl carrier protein in the fatty acid synthase complex. SYN: pantetheine 4′-phosphate.
Low serum phosphate levels. SYN: phosphorpenia. [phospho- + G. penia, poverty]
phosphopentose epimerase (fos-fo-pen′tos e-pim-er-as)
An enzyme that catalyzes the reversible epimerization of a number of phosphorylated, five-carbon sugars; most notably ribulose 5-phosphate to xylulose 5-phosphate in the pentose phosphate pathway.
phosphopentose isomerase (fos-fo-pen′tos)
SYN: ribose 5-phosphate isomerase.
A protein (MW 155,000) found in dentin that is believed to have a role in mineralization.
A protein containing phosphoryl groups attached directly to the side chains of some of its constituent amino acids, usually to the hydroxyl group of an l-seryl residue or an l-threonyl residue; e.g., casein, vitellin, ovalbumin.
phosphopyruvate hydratase (fos-fo-pi′roo-vat)
1. A chemical substance that transforms incident electromagnetic or radiation energy into light, as in scintillation radioactivity determinations or radiographic intensifying screens or image amplifiers. 2. Any substance capable of exhibiting phosphorescence. [G. phos, light, + phoros, bearing] photostimulable p. the chemical coating the p. plate in a computed radiography system; the latent image is recovered by laser scanning.
Forming a compound with phosphorus.
The quality or property of emitting light without active combustion or the production of heat, generally as the result of prior exposure to radiation, which persists after the inciting cause is removed. [G. phos, light, + phoros, bearing]
Having the property of phosphorescence.
The excretion of luminous sweat. SYN: phosphoridrosis. [G. phos, light, + phoros, bearing, + hidrosis, sweating]
SYN: ribose 5-phosphate isomerase.
An intermediate in purine biosynthesis.
phosphoribosylglycineamide synthetase (fos′fo-ri′bo-sil-gli-sin′a-mid)
Glycinamide ribonucleotide synthetase;an enzyme that reacts glycine with ribosylamine 5-phosphate and ATP to form ADP, orthophosphate, and phosphoribosylglycineamide in the course of purine biosynthesis.
5-phospho-α-d-ribosyl-1-pyrophosphate (PPRibp, PPRP, PRPP)
5-Phosphoribosyl 1-diphosphate;d-ribose carrying a phosphate group on ribose carbon-5 and a pyrophosphate group on ribose carbon-1; an intermediate in the formation of the pyrimidine and purine nucleotides as well as NAD+. SYN: 5-phosphoribose 1-diphosphate.
One of a group of enzymes (EC 2.4.2.x, pentosyltransferases) that transfers d-ribose 5-phosphate from 5-phospho-α-d-ribosyl pyrophosphate to a purine, pyrimidine, or pyridine acceptor, forming a 5′-nucleotide and pyrophosphate, or d-ribose from d-ribosyl phosphate to a base, forming a nucleoside, or similar pentose transfers; important in nucleotide biosynthesis. Specific phosphoribosyltransferases are preceded by the name of the acceptor base, e.g., uracil p. ( i.e., uracil + PRPP &rrl; UMP + pyrophosphate).
An enzyme that, in the presence of ATP, catalyzes the phosphorylation of d-ribulose 5-phosphate to d-ribulose 1,5-bisphosphate and ADP, a reaction of importance in the carbon dioxide fixation cycle of photosynthesis.
phosphoribulose epimerase (fos-fo-ri′bu-los)
SYN: ribulose-phosphate 3-epimerase.
phosphoric acid (fos-for′ik)
Orthophosphoric acid; a strong acid of industrial importance; m.p. 42.35°C; dilute solutions have been used as urinary acidifiers and as dressings to remove necrotic debris. In dentistry, it constitutes about 60% of the liquid used in zinc phosphate and silicate cements; solutions in varying concentrations are used for etching enamel and dentin surfaces prior to applications of various types of resins. cyclic p. 1. in general, a linear polymer of p. residues in pyrophosphate linkage in which the α and ω residues are similarly linked to make one endless loop or cyclic compound; 2. specifically, a generic term applied to compounds in which one p. residue is esterified to two hydroxyl groups of a single carbon chain, as in adenosine 3′,5′-p., adenosine 2′,3′-p., etc. dilute p. a solvent containing 10% H3PO4. glacial p. an anhydride of p. used as a reagent and in the manufacture of zinc oxyphosphate cement for dentistry. SYN: metaphosphoric acid.
Chronic poisoning with phosphorus.
A reaction analogous to hydrolysis except that the elements of phosphoric acid, rather than of water, are added in the course of splitting a bond; e.g., the formation of glucose 1-phosphate from glycogen. SYN: phosphoroclastic cleavage.
phosphorous (fos′for-us, fos-for′us)
1. Relating to, containing, or resembling phosphorus. 2. Referring to phosphorus in its lower (+3) valence state.
H3PO3;its salts are phosphites.
phosphorus (P) (fos′for-us)
A nonmetallic chemical element, atomic no. 15, atomic wt. 30.973762, occurring extensively in nature always in combination as phosphates, phosphites, etc., and as the phosphate in every living cell; the elemental form is extremely poisonous, causing intense inflammation and fatty degeneration; repeated inhalation of p. fumes may cause necrosis of the jaw (phosphonecrosis); the approximate fatal dose is 50–100 mg. [G. phosphoros, fr. phos, light, + phoros, bearing] amorphous p., red p. an allotropic form of p. formed by heating ordinary p., in the absence of oxygen, to 260°C; it occurs as an amorphous dark red mass or powder, nonpoisonous, and much less flammable than ordinary p.; it may be reconverted to the latter by heating to 454.4°C in nitrogen gas. p. pentoxide the ultimate anhydride of orthophosphoric acid; a drying and dehydrating agent; corrosive.
Radioactive phosphorus isotope; beta emitter with half-life of 14.28 days; used as tracer in metabolic studies and in the treatment of certain diseases of the osseous and hematopoietic systems.
A radioactive isotope of phosphorus with a half-life of 25.3 days; used as a tracer in metabolic studies.
The radical, O&dbond;P&cbond;, as in p. chloride, POCl3.
Prefix incorrectly used to signify a phosphate ( e.g., phosphorylcholine) in place of the correct O-phosphono- or phospho-.
A phosphorylated enzyme cleaving poly(1,4-α-d-glucosyl)n with orthophosphate to form poly(1,4-α-d-glucosyl)n−1 and α-d-glucose 1-phosphate. SYN: α-glucan p., glycogen p., P enzyme, p. a, polyphosphorylase. p. a SYN: p.. p. b dephosphorylated p. a. Under most conditions, the inactive form of p.; active in the presence of AMP. See p. phosphatase. p. kinase an enzyme that uses ATP to phosphorylate p. b and thus reform p. a, the active form of p.; the active form of p. kinase is itself a phosphorylated protein; upon dephosphorylation of p. kinase, the enzyme is inactivated; it can be rephosphorylated with a cAMP-dependent protein kinase; p. kinase is deficient in certain types of glycogen storage disease. p. phosphatase an enzyme catalyzing the conversion of one p. a into two p. b, with the release of four orthophosphates. SYN: p.-rupturing enzyme.
1. General term for enzymes transferring a phosphoryl group to some organic acceptor, hence belonging to the transferases. 2. Specifically, enzymes that release a single glucosyl residue from a polyglucose as d-glucose 1-phosphate, the phosphate coming from orthophosphate; e.g., phosphophorylase, sucrose p., cellobiose p.. nucleoside p. enzymes that catalyze the phosphorolysis of a nucleoside, forming the free purine or pyrimidine plus ribose (or deoxyribose 1-phosphate); e.g., purine-nucleoside p..
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