title: Subcellular site of biosynthesis of the catecholamine biosynthetic enzymes in bovine adrenal medulla.
abstract: The subcellular site of biosynthesis of the catecholamine biosynthetic enzymes was examined. Free and membrane-bound polysomes were prepared from bovine adrenal medulla and mRNA was isolated from these polysomes. Both were active in directing cell-free translations. Immunoprecipitation of cell-free products with specific antisera localized the biosynthesis of the subunits of tyrosine hydroxylase (TH) (apparent Mr = 61,000) and of phenylethanolamine N-methyltransferase (PNMT) (apparent Mr = 32,000) on free polysomes, compared with biosynthesis of subunits of dopamine beta-hydroxylase (DBH) (apparent Mr = 67,000) on membrane-bound polysomes. Cross-reactivity between translation products was observed. Antibodies for DBH recognized a polypeptide with electrophoretic mobility identical to newly synthesized PNMT. However increasing concentrations of antibodies to DBH recognized at most 1/20 of the PNMT formed. The results of this study show the subcellular distribution of the catecholamine synthesizing enzymes is determined by their site of biosynthesis.
mesh_terms: D000313:Adrenal Medulla / Q000201:enzymology* / Q000648:ultrastructure; D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D004299:Dopamine beta-Hydroxylase / Q000096:biosynthesis*; D007163:Immunosorbent Techniques; D046911:Macromolecular Substances; D010625:Phenylethanolamine N-Methyltransferase / Q000096:biosynthesis*; D011132:Polyribosomes / Q000201:enzymology*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000096:biosynthesis*
chemical_list: D046911:Macromolecular Substances; D012333:RNA, Messenger; D014446:Tyrosine 3-Monooxygenase; D004299:Dopamine beta-Hydroxylase; D010625:Phenylethanolamine N-Methyltransferase