NADPH production by the pentose phosphate pathway in the zona fasciculata of rat adrenal gland. 2007

Wilma M Frederiks, and Intan P E D Kümmerlin, and Klazina S Bosch, and Heleen Vreeling-Sindelárová, and Ard Jonker, and Cornelis J F Van Noorden
Department of Cell Biology & Histology, Academic Medical Center, Amsterdam, The Netherlands.

Biosynthesis of steroid hormones in the cortex of the adrenal gland takes place in smooth endoplasmic reticulum and mitochondria and requires NADPH. Four enzymes produce NADPH: glucose-6-phosphate dehydrogenase (G6PD), the key regulatory enzyme of the pentose phosphate pathway, phosphogluconate dehydrogenase (PGD), the third enzyme of that pathway, malate dehydrogenase (MDH), and isocitrate dehydrogenase (ICDH). However, the contribution of each enzyme to NADPH production in the cortex of adrenal gland has not been established. Therefore, activity of G6PD, PGD, MDH, and ICDH was localized and quantified in rat adrenocortical tissue using metabolic mapping, image analysis, and electron microscopy. The four enzymes have similar localization patterns in adrenal gland with highest activities in the zona fasciculata of the cortex. G6PD activity was strongest, PGD, MDH, and ICDH activity was approximately 60%, 15%, and 7% of G6PD activity, respectively. The K(m) value of G6PD for glucose-6-phosphate was two times higher than the K(m) value of PGD for phosphogluconate. As a consequence, virtual flux rates through G6PD and PGD are largely similar. It is concluded that G6PD and PGD provide the major part of NADPH in adrenocortical cells. Their activity is localized in the cytoplasm associated with free ribosomes and membranes of the smooth endoplasmic reticulum, indicating that NADPH-demanding processes related to biosynthesis of steroid hormones take place at these sites. Complete inhibition of G6PD by androsterones suggests that there is feedback regulation of steroid hormone biosynthesis via G6PD.

UI MeSH Term Description Entries
D007521 Isocitrate Dehydrogenase An enzyme of the oxidoreductase class that catalyzes the conversion of isocitrate and NAD+ to yield 2-ketoglutarate, carbon dioxide, and NADH. It occurs in cell mitochondria. The enzyme requires Mg2+, Mn2+; it is activated by ADP, citrate, and Ca2+, and inhibited by NADH, NADPH, and ATP. The reaction is the key rate-limiting step of the citric acid (tricarboxylic) cycle. (From Dorland, 27th ed) (The NADP+ enzyme is EC 1.1.1.42.) EC 1.1.1.41. NAD Isocitrate Dehydrogenase,Isocitrate Dehydrogenase (NAD+),Isocitrate Dehydrogenase-I,Dehydrogenase, Isocitrate,Dehydrogenase, NAD Isocitrate,Isocitrate Dehydrogenase I,Isocitrate Dehydrogenase, NAD
D008291 Malate Dehydrogenase An enzyme that catalyzes the conversion of (S)-malate and NAD+ to oxaloacetate and NADH. EC 1.1.1.37. Malic Dehydrogenase,NAD-Malate Dehydrogenase,Dehydrogenase, Malate,Dehydrogenase, Malic,Dehydrogenase, NAD-Malate,NAD Malate Dehydrogenase
D008297 Male Males
D008854 Microscopy, Electron Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen. Electron Microscopy
D009243 NAD A coenzyme composed of ribosylnicotinamide 5'-diphosphate coupled to adenosine 5'-phosphate by pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH). (Dorland, 27th ed) Coenzyme I,DPN,Diphosphopyridine Nucleotide,Nadide,Nicotinamide-Adenine Dinucleotide,Dihydronicotinamide Adenine Dinucleotide,NADH,Adenine Dinucleotide, Dihydronicotinamide,Dinucleotide, Dihydronicotinamide Adenine,Dinucleotide, Nicotinamide-Adenine,Nicotinamide Adenine Dinucleotide,Nucleotide, Diphosphopyridine
D010427 Pentose Phosphate Pathway An oxidative decarboxylation process that converts GLUCOSE-6-PHOSPHATE to D-ribose-5-phosphate via 6-phosphogluconate. The pentose product is used in the biosynthesis of NUCLEIC ACIDS. The generated energy is stored in the form of NADPH. This pathway is prominent in tissues which are active in the synthesis of FATTY ACIDS and STEROIDS. Hexose Monophosphate Shunt,Pentose Phosphate Shunt,Pentose Shunt,Pentosephosphate Pathway,Pentose-Phosphate Pathway,Pentosephosphate Shunt,Hexose Monophosphate Shunts,Pathway, Pentose Phosphate,Pathway, Pentose-Phosphate,Pathway, Pentosephosphate,Pathways, Pentose Phosphate,Pathways, Pentose-Phosphate,Pathways, Pentosephosphate,Pentose Phosphate Pathways,Pentose Phosphate Shunts,Pentose Shunts,Pentose-Phosphate Pathways,Pentosephosphate Pathways,Pentosephosphate Shunts,Shunt, Hexose Monophosphate,Shunt, Pentose,Shunt, Pentose Phosphate,Shunt, Pentosephosphate,Shunts, Hexose Monophosphate,Shunts, Pentose,Shunts, Pentose Phosphate,Shunts, Pentosephosphate
D010734 Phosphogluconate Dehydrogenase An enzyme of the oxidoreductase class that catalyzes the reaction 6-phospho-D-gluconate and NADP+ to yield D-ribulose 5-phosphate, carbon dioxide, and NADPH. The reaction is a step in the pentose phosphate pathway of glucose metabolism. (From Dorland, 27th ed) EC 1.1.1.43. 6-Phosphogluconate Dehydrogenase,6 Phosphogluconate Dehydrogenase,Dehydrogenase, 6-Phosphogluconate,Dehydrogenase, Phosphogluconate
D005954 Glucosephosphate Dehydrogenase Glucose-6-Phosphate Dehydrogenase,Dehydrogenase, Glucose-6-Phosphate,Dehydrogenase, Glucosephosphate,Glucose 6 Phosphate Dehydrogenase
D000738 Androsterone A metabolite of TESTOSTERONE or ANDROSTENEDIONE with a 3-alpha-hydroxyl group and without the double bond. The 3-beta hydroxyl isomer is epiandrosterone. 3-alpha-Hydroxy-5-alpha-Androstan-17-One,5 alpha-Androstan-3 alpha-ol-17-one,Epiandrosterone,3 alpha Hydroxy 5 alpha Androstan 17 One,5 alpha Androstan 3 alpha ol 17 one
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia

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