Subcellular Site of Biosynthesis of the Catecholamine Biosynthetic Enzymes in Bovine Adrenal Medulla |
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Authors: | Esther L Sabban Menek Goldstein |
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Institution: | Department of Biochemistry, New York Medical College, Valhalla, New York;Neurochemistry Laboratories, Department of Psychiatry, New York University Medical Center, New York, New York, U.S.A. |
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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. |
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Keywords: | Tyrosine hydroxylase Phenylethanolamine N-methyltransferase Dopamine β-hydroxylase Polysomes Translation Adrenal medulla |
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