Localization of oleic acid biosynthesis enzymes in the proplastids of developing castor endosperm

Abstract

The particulate fatty acid synthesizing system from the developing castor bean endosperm was separated using sucrose density gradients. The particulate fatty acid synthesizing enzymes were associated with a particle of peak density 1.21 g∙(cm3)−1. Based on the presence of triosephosphate isomerase and the appearance of the particles in electron micrographs the major constituent of this fraction was identified as proplastids. It appears that in this tissue the proplastid contains the complete enzyme complement for oleic acid synthesis from acetyl or malonyl-CoA.