| cyclic nucleotide | A nucleoside monophosphate in which the phosphoryl group is linked twice to the sugar moiety; e.g., adenosine 3',5'-cyclic monophosphate (cAMP). (05 Mar 2000) |
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| cyclic nucleotide-regulated protein kinases | <enzyme> A group of enzymes that catalyses the phosphorylation of serine or threonine residues of proteins and is dependent on cyclic nucleotides. Registry number: EC 2.7.10.- (12 Dec 1998) |
| cyclic peptide | A peptide that forms a ring structure; e.g., tyrocidin A, an antibiotic, is a cyclic decapeptide; valinomycin is a cyclic depsipeptide. (05 Mar 2000) |
| cyclic phosphate | An activator of phosphorylase kinase and an effector of other enzymes, formed in muscle from ATP by adenylate cyclase and broken down to 5'-AMP by a phosphodiesterase; sometimes referred to as the "second messenger." A related compound (2',3') is also known. Synonym: cyclic adenylic acid, cyclic AMP, cyclic phosphate. Acronym: cAMP (05 Mar 2000) |
| cyclic phosphoric acid | In general, a linear polymer of phosphoric acid residues in pyrophosphate linkage in which the a and ω residues are similarly linked to make one endless loop or cyclic compound, specifically, a generic term applied to compounds in which one phosphoric acid residue is esterified to two hydroxyl groups of a single carbon chain, as in adenosine 3',5'-phosphoric acid, adenosine 2',3'-phosphoric acid, etc. (05 Mar 2000) |
| cyclic phosphorylation | Any process in which a phosphatide ester forms a cylic diester by linkage to a neighbouring hydroxyl group. (18 Nov 1997) |
| cyclic photophosphorylation | Process by which light energy absorbed by photosystem I in the chloroplast can be used to generate ATP without concomitant reduction of NADP or other electron acceptors. Energised electrons are passed from PS I to ferredoxin and thence along a chain of electron carriers and back to the reaction centre of PS I, generating ATP en route. (18 Nov 1997) |
| cyclic strabismus | A strabismus that appears and disappears in rhythym, most frequently at 48-hour intervals. (05 Mar 2000) |
| cyclic uridine 3',5'-monophosphate | A cyclic nucleotide involved in metabolic regulation; inhibits the growth of some tumours. (05 Mar 2000) |
| cyclin | <protein> Proteins (A and B forms known) whose levels in a cell varies markedly during the cell cycle, rising steadily until mitosis, then falling abruptly to zero. As cyclins reach a threshold level, they are though to drive cells into G2 phase and thus to mitosis. Cyclins combine with p34 kinase (cdc2) to form maturation-promoting factor (MPF). See: M phase promoting factor. (18 Nov 1997) |
| cyclin a | A 33-kD protein identical to adenovirus e1a-associated protein p60. Cyclin a regulates p33cdk2 and p34cdc2, and is necessary for progression through the s phase of the cell cycle. (12 Dec 1998) |
| cyclin b | A 58-kD protein that is regulated post-transcriptionally and post-translationally in the cell cycle. (12 Dec 1998) |
| cyclin d1 | Protein encoded by the bcl-1 gene which plays a critical role in regulating the cell cycle. Overexpression of cyclin d1 is the result of bcl-1 rearrangement, a t(11;14) translocation, and is implicated in various neoplasms. (12 Dec 1998) |
| cyclin e | A 50-kD protein that complexes with cdk2 in the late g1 phase of the cell cycle. (12 Dec 1998) |
| cyclin E-dependent kinase | <chemical> Synonym: cyce-h1k, cyce-dependent h1 kinase (26 Jun 1999) |