| 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) |
| meso- | Mes- 1. Middle, mean, intermediacy. 2. A mesentery, mesentery-like structure. 3. A prefix denoting a compound, containing more than one chiral centre, having an internal plane of symmetry; such compounds do not exhibit optical activity (e.g., meso-cystine). Origin: G. Mesos (05 Mar 2000) |
| meso compound | <chemistry> A compound that has two or more chiral centres but does not rotate plane-polarized light because it has an internal plane of symmetry. These compounds are identical to their mirror images. (09 Jan 1998) |
| meso compounds | Compounds containing more than one asymmetric carbon atom, with configurations about them so balanced that the molecule as a whole possesses a plane of symmetry, although the individual carbon atoms do not; such compounds are not optically active; e.g., ribitol, mucic acid, meso-inositol, meso-cystine. (05 Mar 2000) |
| meso-cystine | An isomer of cystine in which the configuration about one of the alpha-carbons is d, about the other, l, so that the molecule as a whole possesses a plane of symmetry and is optically inactive. Note that meso-cystine is not dl-cystine. Dl-cystine is a racaemic mixture of dd-cystine and ll-cystine. (05 Mar 2000) |
| meso-inositol | 1. Generic term for any isomer of meso-inositol in which the hydroxyl groups are so arranged that the molecule as a whole possesses a plane of symmetry and is optically inactive. 2. Former name for myo-inositol. (05 Mar 2000) |
| meso-ontomorph | A broad, stocky individual. Origin: meso-+ G. On, being, + morphe, form (05 Mar 2000) |
| meso-tartrate dehydrogenase | <enzyme> Forms dihydroxyfumarate; distinguished from EC 1.1.1.93 which forms oxaloglycollate Registry number: EC 1.3.1.7 (26 Jun 1999) |
| 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) |