TY - JOUR
T1 - NADPH production by the pentose phosphate pathway in the zona fasciculata of rat adrenal gland
AU - Frederiks, Wilma M.
AU - Kümmerlin, Intan P. E. D.
AU - Bosch, Klazina S.
AU - Vreeling-Sindelárová, Heleen
AU - Jonker, Ard
AU - van Noorden, Cornelis J. F.
PY - 2007
Y1 - 2007
N2 - 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 similar to 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
AB - 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 similar to 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
U2 - https://doi.org/10.1369/jhc.7A7222.2007
DO - https://doi.org/10.1369/jhc.7A7222.2007
M3 - Article
C2 - 17533217
SN - 0022-1554
VL - 55
SP - 975
EP - 980
JO - Journal of Histochemistry and Cytochemistry
JF - Journal of Histochemistry and Cytochemistry
IS - 9
ER -