Figure 6: Leucine supplementation recovers leucine⁺ phenotype while isoleucine supplementation does not.

The ability of leucine or isoleucine supplementation to complement the leucine⁺ phenotype in the (a) pex10 mfe1 leucine⁻ uracil⁺ DGA1 and the (b) PO1f leucine⁻ uracil⁺ backgrounds was tested. Leucine (1.6 g l⁻¹) supplementation complemented the leucine⁺ phenotype in both the pex10 mfe1 leucine⁻ uracil⁺ DGA1 and the PO1f leucine⁻ uracil⁺ backgrounds. Leucine supplementation had no effect on the pex10 mfe1 leucine⁺ uracil⁺ DGA1 background or the PO1f leucine⁺ uracil⁺ backgrounds, demonstrating the leucine biosynthetic capacity generates enough leucine to stimulate lipogenesis. Isoleucine had no effect on lipogenesis in either the leucine⁺ or leucine⁻ backgrounds. Thus, the benefit of leucine towards lipogenesis is not a result of leucine catabolism for carbon and nitrogen use. Error bars represent s.d. of biological triplicates.