Role of Elongase Reactions in LCPUFA Synthesis Figure 3. Examination of product/substrate relationships for elongation by Elovl5 and Elovl2. Recombinant S. cerevisiae expressing empty pYES2 vector or Elovl5 were grown in the presence of EPA (A) or recombinant S. cerevisiae expressing empty pYES2 vector or Elovl2 were grown in the presence of EPA (B) or DPA (C). Fatty acids were extracted from the recombinant S. cerevisiae and the amount of each fatty acid was quantified in mg g21 of S. cerevisiae. The results are the means 6 S.D. of triplicate incubations. Values with different symbols are significantly different from each other. doi:10.1371/journal.pone.0029662.g003 potential for competitive substrate inhibition. Although SDA and EPA are both Elovl5 substrates, there was no evidence to suggest n-3 PUFA competition between substrates at the concentrations used in this study. Luthria and Sprecher [9] reported that neither EPA nor DPA inhibited SDA elongation in rat liver microsomes, although at the time they were unaware of which elongase enzyme PLoS ONE | www.plosone.org 4 December 2011 | Volume 6 | Issue 12 | e29662