Message de kate
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Pouh........un gros message histoire de citer quelques sources (il y en a plein d'autres) :
Métabolisme périphérique du cortisol surrénalien :
Extrait de :
http://en.wikipedia.org/wiki/Cortisol
Cortisol is metabolized by the 11-beta hydroxysteroid dehydrogenase system (11-beta HSD), which consists of two enzymes: 11-beta HSD1 and 11-beta HSD2.
11-beta HSD1 utilizes the cofactor NADPH to convert biologically-inert cortisone to biologically-active cortisol
11-beta HSD2 utilizes the cofactor NAD+ to convert cortisol to cortisone
Overall, the net effect is that 11-beta HSD1 serves to increase the local concentrations of biologically-active cortisol in a given tissue; 11-beta HSD2 serves to decrease local concentrations of biologically-active cortisol.
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NADPH :
Extrait de :
http://fr.wikipedia.org/wiki/Nicotinami ... _phosphate
Au niveau du métabolisme, le NADPH est principalement produit par la phase oxydative de la voie des pentoses phosphates. Le NADPH est la source principale d'électrons utilisés dans les réactions biosynthétiques dans la cellule. Il est également utilisé dans les mécanismes de protection contre le stress oxydant et les espèces réactives de l'oxygène (ROS). La détoxication de ces espèces réactives fait intervenir le glutathion qui doit être régénéré constamment par la glutathion réductase suivant le schéma suivant :
GSSG + NADPH + H+ → 2 GSH + NADP+
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G6PD et NADPH :
Extrait de :
http://rialto.com/g6pd/fig3.htm
FIGURE 3 The Pentose Phosphate Pathway. Note the importance of G6PD in the production of reduced G-SH, ribose, and NADPH (adapted from: Yoshida and Beutler, 1986, pg.8).
NADP+ = nicotinamide adenine dinucleotide phosphate
NADPH = reduced nicotinamide adenine dinucleotide phosphate
GS-SG = oxidized glutathione
G-SH = reduced glutathione
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G6PD et NADPH :
Extraits de :
http://flipper.diff.org/app/pathways/info/2101
Glucose-6-phosphate dehydrogenase is a cytosolic enzyme in the pentose phosphate pathway, a metabolic pathway that supplies reducing energy to cells (such as erythrocytes) by maintaining the level of the co-enzyme nicotinamide adenine dinucleotide phosphate (NADPH). The NADPH in turn maintains the level of glutathione in these cells that helps protect the red blood cells against oxidative damage. Of greater quantitative importance is the production of NADPH for tissues actively engaged in biosynthesis of fatty acids and/or isoprenoids, such as the liver, mammary glands, adipose tissue, and the adrenal glands. It is notable in humans when there is a genetic deficiency which predisposes to non-immune haemolytic anaemia. In higher plants, several isoforms of G6PDH have been reported, which are localized in the cytosol, the plastidic stroma, and peroxisomes.
G6PD is also responsible for maintaining adequate levels of NADPH inside the cell. NADPH is a required cofactor in many biosynthetic reactions. NADPH is also used to keep glutathione, a tri-peptide, in its reduced form.
The enzyme, glucose-6-phosphate dehydrogenase (G6PDH, EC1.1.1.49), has long been considered and studied as the archetypical X-linked "housekeeping" enzyme that is present in all cells, where it plays the key role in regulating carbon flow through the pentose phosphate pathway. Specifically, the enzyme catalyzes the first reaction in the pathway leading to the production of pentose phosphates and reducing power in the form of NADPH for reductive biosynthesis and maintenance of the redox state of the cell. It was in this latter function that the crucial importance of the enzyme was first appreciated with the descrïption of the human deficiency syndrome. While the gene can be considered to be a constitutively expressed "housekeeping" gene in many tissues, there are several other tissues (liver, adipose, lung, and proliferating cells) wherein modulation of cellular G6PDH activity represents an important component of the integrated response to external stimuli (hormones, growth factors, nutrients, and oxidant stress). In this regard, adaptive regulation of G6PDH has been found to be exerted at transcrïptional and posttranscrïptional levels.
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Organismes possédant l'enzyme G6PD :
http://www.brenda-enzymes.org/php/resul ... o=1.1.1.49
G6PD Aspergillus aculeatus - 674379
G6PD Bos indicus - 686342
G6PD Bos taurus - 697523
G6PD Canis lupus familiaris - 655736
G6PD Coriandrum sativum - 656419
G6PD Drosophila melanogaster - 698837
G6PD Homo sapiens - 655123, 656387, 672382, 672702, 673944, 686131, 688050, 689915, 696447, 696962, 697523, 698392, 699960
G6PD Meleagris gallopavo - 655712
G6PD Mus musculus - 671386, 697311, 697523
G6PD Oncorhynchus mykiss - 673169, 675104, 700590
G6PD Ovis aries - 656382, 686208, 701169
G6PD Petroselinum crispum - 657147
G6PD Pichia guilliermondii - 676917
G6PD Polygonum cognatum - 695961
G6PD Rattus norvegicus - 655495, 656430, 657284, 697523
G6PD Saccharomyces cerevisiae - 685541, 686448, 697523
G6PD Thermotoga maritima - 655612
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G6PD dans les feuilles de Coriandrum Sativum :
http://cat.inist.fr/?aModele=afficheN&cpsidt=15789748
Glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP+ oxidoreductase, EC 1.1.1.49; G6PD) was purified from coriander (Coriandrum sativum) leaves;