| gamma-glutamate (glutamate gamma-) carboxypeptidase | N-Pteroyl-l-glutamate hydrolase;an enzyme cleaving l-glutamyl residues from pteridine oligoglutamates; used in certain antitumour treatments. Synonym: carboxypeptidase G, conjugase, gamma-glutamate (glutamate gamma-) carboxypeptidase. (05 Mar 2000) |
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| phospholipase | <enzyme> That hydrolyse ester bonds in phospholipids. They comprise two types: aliphatic esterases (phospholipase A1, A2 and B) that release fatty acids and phosphodiesterases (types C and D) that release diacyl glycerol or phosphatidic acid respectively. Type A2 is widely distributed in venoms and digestive secretions. Types A1, A2 and C the latter specific for phosphatidyl inositol) are present in all mammalian tissues. Type C is also found as a highly toxic secretion product of pathogenic bacteria. Type B attacks monoacyl phospholipids and is poorly characterised. Type D is largely of plant origin. PLA2 Type II (a secreted enzyme, but not the same as the Type I digestive pancreatic enzyme) is probably very important in inflammation because its action can release arachidonic acid, the starting point for eicosanoid synthesis. Phosphatidyl inositol bisphosphate specific phospholipase C is important in generating diacyl glycerol and inositol trisphosphate, both second messengers. (31 Dec 1997) |
| phospholipase A1 | <enzyme> An enzyme that hydrolyzes a lecithin (1,2-diacylglycerophosphocholine) to a 2-acylglycerophosphocholine and a fatty acid anion. (05 Mar 2000) |
| phospholipase A2 | <enzyme> An enzyme that catalyses 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. Synonym: lecithinase A, phosphatidase, phosphatidolipase. (05 Mar 2000) |
| phospholipase B | There are reports that phospholipase B is a mixture of phospholipase A1 and phospholipase A2. See: lysophospholipase. (05 Mar 2000) |
| phospholipase c | <enzyme> An enzyme found in the alpha-toxin of clostridium welchii and other strains of clostridia and bacilli. It hydrolyzes glycerophosphatidates with the formation of 1,2-diacylglycerol and a phosphorylated nitrogenous base such as choline. Chemical name: Phosphatidylcholine cholinephosphohydrolase Registry number: EC 3.1.4.3 (12 Dec 1998) |
| phospholipase d | <enzyme> An enzyme found mostly in plant tissue. It hydrolyzes glycerophosphatidates with the formation of a phosphatidic acid and a nitrogenous base such as choline. This enzyme also catalyses transphosphatidylation reactions. Chemical name: Phosphatidylcholine phosphatidohydrolase Registry number: EC 3.1.4.4 (12 Dec 1998) |
| bis-gamma-glutamylcystine reductase | <enzyme> From halobacterium halobium; specific for NADPH Registry number: EC 1.6.4.- Synonym: bis-ggc reductase (26 Jun 1999) |
| gamma | <physics> Third letter in the Greek alphabet, variable used for a number of things in physics, in plasma physics gamma is often used as the variable for growth rates of instabilities. (09 Oct 1997) |
| gamma-Abu | gamma-aminobutyric acid |
| gamma alcoholism | Jellinek's term for a severe stage of alcoholism characterised by a progression from psychological to physiological dependence upon alcohol, including tissue dependence and withdrawal symptoms, with loss of control over alcohol intake and destructive effects on interpersonal relationships. (05 Mar 2000) |
| gamma aminobutyric acid | <biochemistry> An important amino acid which functions as the most prevalent inhibitory neurotransmitter in the central nervous system. Gamma aminobutyric acid works in partnership with a derivative of Vitamin B-6, pyridoxine, to cross from the axons to the dendrites through the synaptic cleft, in response to an electrical signal in the neuron and inhibits message transmission. This helps control the nerve cells from firing too fast, which would overload the system. The action of gamma aminobutyric acid decreases epileptic seizures and muscle spasms by inhibiting electrical signals in this manner. Studies have shown that the site of action in the brain of benzodiazepams, including Valium, is directly coupled to the brain receptor for gamma aminobutyric acid. Acronym: GABA (05 Jan 1998) |
| gamma aminobutyric acid receptor | <physiology> Ligand gated chloride ion channel forming receptor opened by gamma aminobutyric acid. Two distinct types: A and B. A receptor: One of a family of neurotransmitter receptors with fast intrinsic ion channels that includes the glycine receptor and the nicotinic acetylcholine receptor. Distinct from another major receptor family, the muscarininc acetylcholine receptor and rhodopsin, with no intrinsic ion channel. The A receptor is specifically blocked by bicuculline. It consists of two pairs of protein chains forming an A2B2 complex, the A chains bind benzodiazepine and the B chains bind GABA. The 4 subunits are thought to form a tight group with the chloride channel in the middle. There is considerable similarity between the amino acid sequences of the receptor subunits and those of the nicotinic acetylcholine receptor suggesting that both receptors are derived from some evolutionary ancestor. See: amino acid receptor superfamily. B receptor: Brain receptor (80 kD) for the inhibitory neurotransmitter gamma amino butyric acid. Differs from the A receptor both in agonist specificity (baclofen is a specific agonist) and its effects on cells. It modulates intracellular calcium levels through a Go mediated effect on N type calcium channels and also lowers intracellular cAMP levels by an effect on adenylyl cyclase, thereby reducing the secretion of catecholamines. (05 Jan 1998) |
| gamma-amylase | A hydrolase removing terminal alpha-1,4-linked d-glucose residues from nonreducing ends of chains, with release of beta-d-glucose. Synonym: acid maltase, amyloglucosidase, gamma-amylase, glucoamylase. (05 Mar 2000) |
| gamma angle | <ophthalmology> The angle formed between a line joining the fixation point to the centre of the eye and the optic axis. (05 Mar 2000) |