| sodium-translocating NADH-quinone reductase | <enzyme> From vibrio alginolyticus; na+ dependent activation is located in the NADH-quinone reductase segment; reduces ubiquinone-1 to ubisemiquinones or ubiquinol; strongly inhibited by 2-n-heptyl-4-hydroxyquinoline n-oxide; do not confuse with sodium independent NADH-quinone reductase EC 1.6.99.2 Registry number: EC 1.6.5.- Synonym: nqr-1, na-translocating NADH-quinone reductase, nqr gene product (26 Jun 1999) |
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| N-acetyldopamine-quinone isomerase | <enzyme> Enzyme from insect cuticle converts n-acetyldopamine quinone to nada quinone methide Registry number: EC 5.3.2.- Synonym: nada-quinone isomerase (26 Jun 1999) |
| NADPH dehydrogenase (quinone) | A flavoprotein similar to NADH dehydrogenase (quinone), but oxidizing NADPH. Synonym: DT-diaphorase, menadione reductase, phylloquinone reductase, quinone reductase. (05 Mar 2000) |
| NAD(p)h dehydrogenase (quinone) | <enzyme> A flavoprotein that reversibly catalyses the oxidation of NADH or NADPH by various quinones and oxidation-reduction dyes. Since the enzyme is a part of the mitochondrial respiratory chain, defects or deficiencies of this enzyme are an important cause of neurological diseases such as parkinsonism. It may have a protective effect against cancer caused by quinones or their metabolic precursors. The enzyme is inhibited by dicoumarol, capsaicin, and caffeine. Chemical name: NAD(P)H:(quinone-acceptor) oxidoreductase Registry number: EC 1.6.99.2 (12 Dec 1998) |
| sulfide quinone reductase | <enzyme> Part of the photosynthetic electron transport chain in chlorobium; reaction occurs in the dark, in the absence of oxygen Registry number: EC 1.8.5.- Synonym: plastoquinone reductase, sulfide-quinone oxidoreductase, sqr enzyme, sulfide-quinone reductase (26 Jun 1999) |
| dopa quinone | An oxidation product of dopa and an intermediate in the formation of melanin from tyrosine. (05 Mar 2000) |
| quinone | Aromatic dicarbonyl compound derived from a dihydroxy aromatic compound. Ubiquinone (coenzyme Q) is a dimethoxy dicarbonyl derivative of benzene involved in electron transport. Other quinones may act as tanning agents. (18 Nov 1997) |
| quinone methide isomerase | <enzyme> From insect cuticle; converts 4-alkyl catechols to quinone methides Registry number: EC 5.3.2.- Synonym: o-quinone-quinone methide isomerase, 4-alkyl-o-quinone-2-hydroxy-4-quinone methide isomerase (26 Jun 1999) |
| quinone methide tautomerase | <enzyme> Enzyme from insect cuticle converts n-acetyldopamine quionone methide to 1,2-dehydro-n-acetyldopamine Registry number: EC 5.3.2.- Synonym: nada quione methide tautomerase (26 Jun 1999) |
| quinone reductase | <enzyme> Enzymes that reduce quinones to phenols usually using NADH or NADPH as a source of reducant. (18 Nov 1997) |
| quinone reductases | <enzyme> NAD(p)h:(quinone acceptor) oxidoreductases. A family that includes three enzymes which are distinguished by their sensitivity to various inhibitors. (NAD(p)h dehydrogenase (quinone)) is a flavoprotein which reduces various quinones in the presence of NADH or NADPH and is inhibited by dicoumarol. (NADH dehydrogenase (quinone)) requires NADH, is inhibited by AMP and 2,4-dinitrophenol but not by dicoumarol or folic acid derivatives. (NADPH dehydrogenase (quinone)) requires NADPH and is inhibited by dicoumarol and folic acid derivatives but not by 2,4-dinitrophenol. Registry number: EC 1.6.99. (12 Dec 1998) |
| anovulatory cycle | A sexual cycle in which no ovum is discharged. (05 Mar 2000) |
| Born-Haber cycle | <physics> This is a mathematical description of the relationship between the electron affinity, heats of atomisation, ionisation energy and lattice energy of ionic compounds. (09 Oct 1997) |
| bottoming cycle | A cogeneration system in which steam is used first for process heat and then for electric power production. (05 Dec 1998) |
| brain wave cycle | The complete upward and downward excursion of a single wave, complex, or impulse as seen on an electroencephalogram. (05 Mar 2000) |