The two molecular weight forms of rat phenylalanine hydroxylase are encoded by different messenger RNAs.
Immunoprecipitation of the phenylalanine hydroxylase formed by translation of rat liver RNA in a rabbit reticulocyte cell-free protein synthesis system was used to examine the origin of the molecular weight heterogeneity of the enzyme. Sodium dodecyl sulfate-polyacrylamide electrophoresis of the immunoprecipitated products showed that in most cases a single specifically immunoprecipitated polypeptide was produced which corresponded to the higher molecular weight (H) form of phenylalanine hydroxylase (Mr = 50,000). The identity of the product was confirmed by immunological competition and peptide mapping. RNA from other rats, however, coded for both the H-form and the lower molecular weight (L) form of phenylalanine hydroxylase or for only the L-form. The evidence suggests that the L-form derives from a different mRNA, rather than by proteolysis of the H-form, an interpretation which is supported by the isolation of the lower form of phenylalanine hydroxylase from livers of some rats.
D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D007527:Isoenzymes / Q000235:genetics*; D008297:Male; D008970:Molecular Weight; D010651:Phenylalanine Hydroxylase / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis*; D051381:Rats; D011919:Rats, Inbred Strains
D007527:Isoenzymes; D012333:RNA, Messenger; D010651:Phenylalanine Hydroxylase