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

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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.