Synthesis of δ‐Aminolaevulinate Synthase in vitro Using Hepatic mRNA from Chick Embryos with Induced Porphyria

Abstract

Polyadenylated mRNA was isolated from chick embryo liver following induction of hepatic porphyria. The RNA was translated in vitro using a wheat germ cell-free system and δ-aminolaevulinate synthase was identified in the translation products by indirect immunoprecipitation. The enzyme was not apparent in the translation products of polyadenylated RNA from non-induced livers. The molecular weight of δ-aminolaevulinate synthase synthesised in vitro was 70000 and the protein was estimated to represent up to 5% of total products synthesised in vitro. These data demonstrate for the first time that induction of chick embryo liver δ-aminolaevulinate synthase activity in hepatic porphyria correlates with a large increase in the translational capacity of isolated polyadenylated RNA for this enzyme and, together with preliminary cDNA · RNA hybridization studies, indicate that an increase in the level of δ-aminolaevulinate synthase mRNA is responsible.