| pentose phosphate cycle | <biochemistry> A pathway of hexose oxidation in which glucose-6-phosphate undergoes two successive oxidations by NADP, the final one being an oxidative decarboxylation to form a pentose phosphate. Diverges from this when glucose-6-phosphate is oxidized to ribose 5 phosphate by the enzyme glucose-6 phosphate dehydrogenase. This step reduces NADP to NADPH, generating a source of reducing power in cells for use in reductive biosyntheses. In plants, part of the pathway functions in the formation of hexoses from carbon dioxide in photosynthesis. Also important as source of pentoses, for example for nucleic acid biosynthesis. This pathway is the main metabolic pathway in neutrophils, congenital deficiency in the pathway produces sensitivity to infection. Alternative metabolic route to Embden Meyerhof pathway for breakdown of glucose. (18 Nov 1997) |
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| pentose phosphate pathway | <biochemistry> A pathway of hexose oxidation in which glucose-6-phosphate undergoes two successive oxidations by NADP, the final one being an oxidative decarboxylation to form a pentose phosphate. Diverges from this when glucose-6-phosphate is oxidized to ribose 5 phosphate by the enzyme glucose-6 phosphate dehydrogenase. This step reduces NADP to NADPH, generating a source of reducing power in cells for use in reductive biosyntheses. In plants, part of the pathway functions in the formation of hexoses from carbon dioxide in photosynthesis. Also important as source of pentoses, for example for nucleic acid biosynthesis. This pathway is the main metabolic pathway in neutrophils, congenital deficiency in the pathway produces sensitivity to infection. Alternative metabolic route to Embden Meyerhof pathway for breakdown of glucose. (18 Nov 1997) |
| reductive dechlorination | Removal of Cl as Cl- from an organic compound by reducing the carbon atom from C-Cl to C H. (09 Oct 1997) |
| 2,3,5,6-tetrachloro-4-hydroquinone reductive dehalogenase | <enzyme> Uses glutathione to dehalogenate 2,3,5,6-tetrachloro-4-hydroquinone to 2,3,6-trichloro-4-hydroquinone and subsequently to 2,6-dichloro-4-hydroquinone; amino acid sequence has been determined; genbank m98559 Registry number: EC 3.8.1.- Synonym: tech reductive dehalogenase, tetrachloro-p-hydroquinone reductive dehalogenase, pcpc gene product, tetrachlorohydroquinone dehalogenase, tchq dehalogenase (26 Jun 1999) |
| pentose | <chemistry> Sugar (monosaccharide) with five carbon atoms. Include ribose and deoxyribose of nucleic acids and many others such as the aldoses arabinose and xylose and the ketoses ribulose and xylulose. (12 Dec 1998) |
| pentose monophosphate shunt | <biochemistry> A pathway of hexose oxidation in which glucose-6-phosphate undergoes two successive oxidations by NADP, the final one being an oxidative decarboxylation to form a pentose phosphate. Diverges from this when glucose-6-phosphate is oxidized to ribose 5 phosphate by the enzyme glucose-6 phosphate dehydrogenase. This step reduces NADP to NADPH, generating a source of reducing power in cells for use in reductive biosyntheses. In plants, part of the pathway functions in the formation of hexoses from carbon dioxide in photosynthesis. Also important as source of pentoses, for example for nucleic acid biosynthesis. This pathway is the main metabolic pathway in neutrophils, congenital deficiency in the pathway produces sensitivity to infection. Alternative metabolic route to Embden Meyerhof pathway for breakdown of glucose. (18 Nov 1997) |
| UDPacetylglucosamine-dolichyl-phosphate acetylglucosamine-1-phosphate transferase | <enzyme> Transfers n-acetylglucosamine 1-phosphate from udp-n-acetylglucosamine to dolichyl phosphate, forming n-acetylglucosaminylpyrophosphoryldolichol Chemical name: udp-glcnac-dolichyl-phosphate glcnac-1-phosphate transerase Registry number: EC 2.7.8.15 Synonym: n-acetylglucosamine-1-phosphate transferase, dol-p-p-glcnac synthase, dolichol pathway enzyme I, udp-acetylglucosamine-dolichol phosphate acetylglucosamine-1-phosphate transferase, glcnac-dp-1-phosphotransferase, udp-n-acetyl-d-glucosamine-dolichyl-phosphate n-acetyl-d-glucosaminephosphotransferase, dolichol-p-dependent n-acetylglucosamine-1-phosphate transferase, alg7 gene product (26 Jun 1999) |
| UDP-GlcNAc-undecaprenyl phosphate N-acetylglucosaminyl 1-phosphate transferase | <enzyme> Catalyses transfer of n-acetylglucosamine 1-phosphate from udp-glcnac to undecaprenyl phosphate Registry number: EC 2.7.8.- Synonym: glcnac-p-p-und synthase, gpt enzyme (26 Jun 1999) |
| 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) |
| c3 cycle | <biochemistry> The part of the photosynthesis process where carbon dioxide is converted into three-carbon compounds, which can then be turned into six-carbon sugars. (07 Nov 1997) |
| c4 cycle | <plant biology> An alternative, very efficient pathway used by plants living in areas with low levels of carbon dioxide, to convert carbon dioxide into a form usable by the plants during photosynthesis. (09 Oct 1997) |
| Calvin Benson cycle | <biochemistry, plant biology> Metabolic pathway responsible for photosynthetic carbon dioxide fixation in plants and bacteria. The enzyme that fixes carbon dioxide is RuDP carboxylase. The cycle is the only photosynthetic pathway in C3 plants and the secondary pathway in C4 plants. The enzymes of the pathway are present in the stroma of the chloroplast. (18 Nov 1997) |