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Dehydrogenases of the pentose phosphate pathway in rat liver peroxisomes
| Content Provider | Scilit |
|---|---|
| Author | Antonenkov, Vasily D. |
| Copyright Year | 1989 |
| Description | Journal: Journal of Biological Inorganic Chemistry Subcellular distribution of pentose-phosphate cycle enzymes in rat liver was investigated, using differential and isopycnic centrifugation. The activities of the $NADP^{+}$-dependent dehydrogenases of the pentose-phosphate pathway (glucose-6-phosphate dehydrogenase and phosphogluconate dehydrogenase) were detected in the purified peroxisomal fraction as well as in the cytosol. Both dehydrogenases were localized in the peroxisomal matrix. Chronic administration of the hypolipidemic drug clofibrate (ethyl-α-p-chlorophenoxysobutyrate) caused a 1.5–2.5-fold increase in the amount of glucose-6-phosphate and phosphogluconate dehydrogenases in the purified peroxisomes. Clofibrate decreased of phosphogluconate dehydrogenase, but did not alter glucose-6-phosphate dehydrogenase activity in the cytosolic fraction. The results obtained indicate that the enzymes of the non-oxidative segment of the pentose cycle (transketolase, transaldolase, triosephosphate isomerase and glucose-phosphate isomerase) are present only in a soluble form in the cytosol, but not in the peroxisomes or other particles, and that ionogenic interaction of the enzymes with the mitochondrial and other membranes takes place during homogenization of the tissue in 0.25 M sucrose. Similar to catalase, glucose-6-phosphate dehydrogenase and phosphogluconate dehydrogenase are present in the intact peroxisomes in a latent form. The enzymes have $K_{m}$ values for their substrates in the millimolar range (0.2 mM for glucose-6-phosphate and 0.10–0.12 mM for 6-phophogluconate). $NADP^{+}$, but not $NAD^{+}$, serves as a coenzyme for both enzymes. Glucose-6-phosphate dehydrogenase was inhibited by palmitoyl-CoA, and to a lesser extent by NADPH. Peroxisomal glucose-6-phosphate and phosphogluconate dehydrogenases have molecular mass of 280 kDa and 96 kDa, respectively. The putative functional role of pentose-phosphate cycle dehydrogenases in rat liver peroxisomes is discussed. |
| Ending Page | 82 |
| Starting Page | 75 |
| ISSN | 2573508X |
| e-ISSN | 14321327 |
| DOI | 10.1111/j.1432-1033.1989.tb14898.x |
| Journal | Journal of Biological Inorganic Chemistry |
| Issue Number | 1 |
| Volume Number | 183 |
| Language | English |
| Publisher | Wiley-Blackwell |
| Publisher Date | 1989-07-01 |
| Access Restriction | Open |
| Subject Keyword | Journal: Journal of Biological Inorganic Chemistry Phosphate Dehydrogenase Pentose Phosphate Phosphate and Phosphogluconate Dehydrogenases |
| Content Type | Text |
| Resource Type | Article |
| Subject | Biochemistry Inorganic Chemistry |
