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Regulation of biogenesis of liver delta-aminolevulinate synthase: effects of structural modifications of heme on the enzyme s RNA Lorber BJ; Ades IZInt J Biochem 1989[]; 21 (4): 439-431. The aim of this study was to determine the effects of several metallo-porphyrins, derived by modifications of heme, on the concentration delta-aminolevulinate (ALA) synthase RNA in hepatocytes. 2. Primary cultures of chick embryo hepatocytes were incubated with allylisopropylacetamide (AIA) for 5 hr in the presence and absence of each metallo-porphyrin (10 microM). At the end of each incubation, total RNA was isolated from the cells and analyzed for ALA synthase-specific RNA by solution hybridization. 3. The concentration of ALA synthase RNA increased 7.3 fold in hepatocytes incubated with AIA alone. The AIA-induced elevations in the enzyme's RNA were blocked partially and equally in cells. incubated with zinc- or with iron-protoporphyrin IX. The block was greater in cells incubated with cobalt-protoporphyrin IX. 4. Modifications of the side chains of the porphyrin ring at positions 2 and 4, giving mesoporphyrin IX and deuteroporphyrin IX, changed the effectiveness of the iron- and the cobalt-porphyrins to limit the AIA-induced increase in ALA synthase RNA. The modifications did not affect the capacities of the zinc-porphyrins to inhibit the rise in RNA. 5. In conclusion, the effect of a given metallo-porphyrin on liver ALA synthase RNA following side chain modification depended on the coordinated metal.|5-Aminolevulinate Synthetase/*biosynthesis[MESH]|Allylisopropylacetamide/pharmacology[MESH]|Animals[MESH]|Cells, Cultured[MESH]|Enzyme Induction/drug effects[MESH]|Heme/*metabolism[MESH]|Hemin/metabolism[MESH]|Liver/*metabolism[MESH]|Metalloporphyrins/pharmacology[MESH]|RNA/*metabolism[MESH]|Structure-Activity Relationship[MESH] |
