Peroxidase biosynthesis as part of protein synthesis by cultured peanut cells

Membrane-bound and free ribosomes from cultured peanut cells were separated by differential centrifugation. The former ribosomes were liberated from the 27000 X g pellet with 1% Triton X100. Purification of both polysome populations was obtained by passage through a 1.5 M sucrose cushion. Both populations have a high rate of protein synthesis in vitro in the presence of a wheat germ S30 fraction. Comparisons of protein synthesis in vitro with that in vivo, and also with labelled proteins released by these cells into the medium did not provide significant information regarding peroxidase biosynthesis. However, immunoprecipitation of the products formed in vitro with antibodies raised against a purified cationic peroxidase fraction, resulted in isolating one major radioactive product. The higher molecular weight of this isolated product compared with the molecular weight of the purified peroxidase fraction suggests the occurrence of a single peptide for peroxidase commensurate with its being a secreted protein.