| carbon-carbon double bond isomerases | <enzyme> Enzymes that catalyze the shifting of a carbon-carbon double bond from one position to another within the same molecule. Registry number: EC 5.3.3 (12 Dec 1998) |
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| carbon-carbon ligases | <enzyme> Enzymes that catalyze the joining of two molecules by the formation of a carbon-carbon bond. These are the carboxylating enzymes and are mostly biotinyl-proteins. Registry number: EC 6.4 (12 Dec 1998) |
| carbon-carbon lyases | <enzyme> Enzymes that catalyze the cleavage of a carbon-carbon bond by means other than hydrolysis or oxidation. This subclass contains the decarboxylases, the aldehyde-lyases, and the oxo-acid-lyases. Registry number: EC 4.1 (12 Dec 1998) |
| asymmetric | Not symmetrical; denoting a lack of symmetry between two or more like parts. (05 Mar 2000) |
| asymmetric centre | <chemistry> Same as a chiral centre, a tetrahedral carbon atom that bears four different substituents. (09 Jan 1998) |
| asymmetric disulfide | <chemistry> Disulfide which is not symmetric on both sides of the -s-s- linkage; e.g., the disulfide formed between coenzyme A and glutathione or between cysteine and coenzyme A or glutathione. Synonym: asymmetric disulfide. (05 Mar 2000) |
| asymmetric motor neuropathy | Neuropathy in which the loss of function is more marked in the extremities of one side of the body, old term for diabetic polyradiculopathy. (05 Mar 2000) |
| active carbon dioxide | Activated carbon dioxide, a complex of N-carboxybiotin (biotin + CO2) and an enzyme; the form in which carbon dioxide is added to other molecules in carboxylations; e.g., to methylcrotonyl-CoA to form beta-methylglutaconyl in the catabolism of leucine, and to acetyl-CoA to form malonyl-CoA. See: acetyl-CoA carboxylase. (05 Mar 2000) |
| anomeric carbon | The reducing carbon of a sugar; C-1 of an aldose, C-2 of a 2-ketose. (05 Mar 2000) |
| arteriovenous carbon dioxide difference | <physiology> The difference in carbon dioxide content (in ml per 100 ml blood) between arterial and venous blood. (05 Mar 2000) |
| carbon | <chemistry, element> Sixth element (Z=6) in the periodic table, has 6 protons, often described as the basis of life on earth because of its chemical properties, has potential for use with silicon as a low-activation structural material for fusion reactors, in the form silicon carbide. Carbon tiles are often used in plasma-facing components because its low Z makes carbon a relatively nice impurity. It is also useful as a neutron moderator. See: low-activation materials, plasma-facing components. Abbreviation: C (13 Nov 1997) |
| carbon-11 | A cyclotron-produced, positron-emitting radioisotope of carbon with a half-life of 20.3 minutes; used in positron-emitting tomography. (05 Mar 2000) |
| carbon-12 | The standard of atomic mass, 98.90% of natural carbon. (05 Mar 2000) |
| carbon-13 | A stable natural isotope, 1.1% of natural carbon. (05 Mar 2000) |
| carbon-14 | A beta-emitter with a half-life of 5715 years, widely used as a tracer in studying various aspects of metabolism; naturally occurring 14C, arising from cosmic ray bombardment, is used to date relics containing natural carbonaceous materials. (05 Mar 2000) |