Elongation systems involved in the biosynthesis of erucic acid from oleic acid in developingBrassica juncea seeds

Abstract In the presence of NADPH and malonyl‐CoA, the cell‐free extract of developing Brassica juncea seeds catalyzes the elongation of 14 C‐oleoyl‐CoA to radioactive C20∶1 and C22∶1. The elongation of C18∶1 to C20∶1 shows no marked preference for NADPH or NADH. On the other hand, the elongation of C20∶1 to C22∶1 exhibits a pronounced preference for NADPH. Moreover, the latter elongation system (C20∶1→C22∶1) is more sensitive to inhibition by trichloroacetate and sodium metabisulfite. Inclusion of polyvinylpolypyrrolidone in the grinding buffer for preparation of the cell‐free extract enhances the elongation activity by 5–6 fold. 14 C‐Stearoyl‐CoA, but not 14 C‐palmitoyl‐CoA, also is elongated by this system. The results presented here suggest certain degrees of dissimilarity between the first (C18∶1→C20∶1) and second elongation (C20∶1→C22∶1) systems.