| nucleoside phosphorylase | <enzyme> From klebsiella sp.; acts on both purine and pyrimidine nucleosides and catalyses the production of araa from uridine arabinoside (arau) and adenine Registry number: EC 2.4.2.- (26 Jun 1999) |
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| nucleoside phosphorylases | Enzymes that catalyze the phosphorolysis of a nucleoside, forming the free purine or pyrimidine plus ribose (or deoxyribose 1-phosphate); e.g., purine-nucleoside phosphorylases. (05 Mar 2000) |
| nucleoside q | <chemical> (1s-(1 alpha,4 beta,5 beta))-2-amino-5-(((4,5-dihydroxy-2-cyclopenten-1-yl)amino)methyl)-1,7-dihydro-7-beta-d-ribofuranosyl-4h-pyrrolo(2,3-d)pyrimidin-4-one. A modified nucleoside which is present in the first position of the anticodon of trna-tyrosine, trna-histidine, trna-asparagine and trna-aspartic acid of many organisms. It is believed to play a role in the regulatory function of trna. Nucleoside q can be further modified to nucleoside q*, which has a mannose or galactose moiety linked to position 4 of its cyclopentenediol moiety. Chemical name: 4H-Pyrrolo(2,3-d)pyrimidin-4-one, 2-amino-5-(((4,5-dihydroxy-2-cyclopenten-1-yl)amino)methyl)-1,7-dihydro-7-beta-D-ribofuranosyl-, (1S-(1alpha,4beta,5beta))- (12 Dec 1998) |
| nucleoside triphosphate | A nucleoside in which the H of one of the ribose hydroxyls (usually the 5') is replaced by a triphosphoric group, -PO(OH)-O-PO(OH)-O-PO(OH)2; e.g., adenosine triphosphate. (05 Mar 2000) |
| nucleoside triphosphate-adenylate kinase | <enzyme> Other nucleoside triphosphates may replace GTP as substrate Registry number: EC 2.7.4.10 Synonym: GTP-AMP phosphotransferase, AMP-GTP phosphotransferase (26 Jun 1999) |
| nucleoside-diphosphate kinase | <enzyme> A phosphotransferase enzyme that is found in mitochondria and in the soluble cytoplasm of cells. It catalyses reversible reactions of a nucleoside triphosphate, e.g., ATP, with a nucleoside diphosphate, e.g., UDP, to form ADP and UTP. Many nucleoside diphosphates can act as acceptor, while many ribonucleoside triphosphates and deoxyribonucleoside triphosphates can act as a donor. Chemical name: ATP:nucleoside-diphosphate phosphotransferase Registry number: EC 2.7.4.6 (12 Dec 1998) |
| nucleoside-diphosphate sugars | Nucleoside diphosphates linked through the 5'-diphosphoric group with simple or complex carbohydrates; e.g., GDP-mannose, UDP-glucose (UDPG), dTDP-glucosamine. (05 Mar 2000) |
| nucleoside-diphosphosugar NAD+ 2-hexosyloxidoreductase | <enzyme> Oxidises udp-galactose to udp-2-ketogalactose Registry number: EC 1.1.1.- (26 Jun 1999) |
| nucleoside-diphosphosugar pyrophosphatase | <enzyme> Catalyses the conversion of xdp-sugar to xmp and sugar 1-phosphate Registry number: EC 3.6.1.- Synonym: ndp-sugar pyrophosphatase, nucleotide-sugar pyrophosphatase (26 Jun 1999) |
| nucleoside-monophosphate | A nucleotide, e.g., AMP. (05 Mar 2000) |
| nucleoside-phosphate kinase | <enzyme> An enzyme that catalyses reversible reactions of a nucleoside triphosphate, e.g., ATP, with a nucleoside monophosphate, e.g., ump, to form ADP and udp. Many nucleoside monophosphates can act as acceptor while many ribo- and deoxyribonucleoside triphosphates can act as donor. Chemical name: ATP:nucleoside-phosphate phosphotransferase Registry number: EC 2.7.4.4 (12 Dec 1998) |
| nucleoside-triphosphatase | <enzyme> Hydrolyzes various nucleotides to a nucleotide diphosphate + pi; inhibited by ca + ATP Registry number: EC 3.6.1.15 Synonym: nucleoside triphosphate phosphohydrolase, nucleoside triphosphatase, ntpase, nuclear envelope nucleoside triphosphatase, nuclear scaffold nucleoside triphosphatase, ns ntpase, nucleosidetriphosphatase (26 Jun 1999) |
| nucleosides | Purine or pyrimidine bases attached to a ribose or deoxyribose. (12 Dec 1998) |
| nucleoskeletal DNA | <molecular biology> DNA that is proposed to exist mostly to maintain nuclear volume and not for coding protein. (18 Nov 1997) |
| nucleosome | <cell biology> Repeating units of organisation of chromatin fibres in chromosomes, consisting of around 200 base pairs and two molecules each of the histones H2A, H2B, H3 and H4. most of the DNA (around 140 base pairs) is believed to be wound around a core formed by the histones, the remainder joins adjacent nucleosomes, thus forming a structure reminiscent of a string of beads. Origin: Gr. Soma = body (18 Nov 1997) |