| hexose | Monosaccharide containing six carbon atoms, for example glucose, galactose, mannose. (18 Nov 1997) |
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| hexose-1-phosphate uridylyltransferase | <enzyme> An enzyme that catalyses the transfer of ump from udpglucose to galactose 1-phosphate, forming udpgalactose and glucose 1-phosphate. Deficiency in this enzyme is the major cause of galactosaemia. Chemical name: UDPglucose:alpha-D-galactose-1-phosphate uridylyltransferase Registry number: EC 2.7.7.12 (12 Dec 1998) |
| hexose monophosphate 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) |
| hexose monophosphate shunt | The main metabolic pathway in activated neutrophils, rendering them relatively insensitive to inhibitors of oxidative phosphorylation. Congenital deficiency of the first enzyme in the shunt, glucose 6 phosphate dehydrogenase, produces a sensitivity to infection similar to that seen in chronic granulomatous disease. (18 Nov 1997) |
| hexose monphosphate pathway | A metabolic pathway present in a wide range of prokaryotic and eukaryotic microorganisms as well as in plants and animals, it involves the oxidative decarboxylation of glucose-6-phosphate, via 6 phosphogluconate, to ribulose 5-phosphate, followed by a series of reversible, non-oxidative interconversions whereby hexose and triose phosphates are formed from pentose phosphates. (09 Oct 1997) |
| hexose phosphatase | <enzyme> May be an aspect of acid phosphatase, EC 3.1.3.2 Registry number: EC 3.1.3.- (26 Jun 1999) |
| hexose phosphate synthetase | <enzyme> Ribulosephosphate formaldehyde gives d-erythro-l-glycero-3-hexulose Registry number: EC 4.1.2.- Synonym: 3-hexulose phosphate synthase, d-arabino-3-hexulose 6-phosphate formaldehyde-lyase, 3-hexulosephosphate synthase, d-arabino-3-hexulose-6-phosphate-lysase, hexulose-6-phosphate synthase, hump synthase (26 Jun 1999) |
| udpglucose-hexose-1-phosphate uridylyltransferase | <enzyme> An enzyme that catalyses the transfer of ump from udpglucose to galactose 1-phosphate, forming udpgalactose and glucose 1-phosphate. Deficiency in this enzyme is the major cause of galactosaemia. Chemical name: UDPglucose:alpha-D-galactose-1-phosphate uridylyltransferase Registry number: EC 2.7.7.12 (12 Dec 1998) |
| utp-hexose-1-phosphate uridylyltransferase | <enzyme> An enzyme that catalyses the synthesis of udpgalactose from utp and galactose-1-phosphate. It is present in low levels in foetal and infant liver, but increases with age, thereby enabling galactosaemic infants who survive to develop the capacity to metabolise galactose. Chemical name: UTP:alpha-D-hexose-1-phosphate uridylyltransferase Registry number: EC 2.7.7.10 (12 Dec 1998) |
| adenosine 5'-diphosphate | A condensation product of adenosine with pyrophosphoric acid, formed from ATP by the hydrolysis of the terminal phosphate group of the latter compound. Acronym: ADP (05 Mar 2000) |
| adenosine diphosphate | <biochemistry> ADP is used as an adenine, a ribose and a diphosphate unit. (06 May 1997) |
| adenosine diphosphate glucose | <chemical> Serves as the glycosyl donor for formation of bacterial glycogen, amylose in green algae, and amylopectin in higher plants. Chemical name: Adenosine 5'-(trihydrogen diphosphate), P'-alpha-D-glucopyranosyl ester (12 Dec 1998) |
| adenosine diphosphate ribose | <chemical> Adenosine 5'-(trihydrogen diphosphate),5'-5-ester with d-ribose. An ester formed between the aldehydic carbon of ribose and the terminal phosphate of adenosine diphosphate. Serves as a ribose carrier. Chemical name: Adenosine 5'-(trihydrogen diphosphate), P'-5-ester with D-ribose (12 Dec 1998) |
| adenosine diphosphate ribose cyclase | <enzyme> Catalyses conversion of nadp to 2'-phospho-cyclic adenosine diphosphoribose; do not use for formation of cyclic adpribose (see ADP-ribosyl cyclase) Registry number: EC 4.6.- Synonym: 2'-p-adpr cyclase (26 Jun 1999) |
| adenosine diphosphate sugars | Esters formed between the aldehydic carbon of sugars and the terminal phosphate of adenosine diphosphate. (12 Dec 1998) |