FIG. 4.

Decomposition of the experimental ¹³C—¹³C scalar-coupling fine structures for the Ile-α and Ile-δ carbons into contributions from the threonine and pyruvate pathways (Fig. 2; Table 2). The stick diagrams represent the fine structures that would be expected if only a single pathway were operational, and the experimental cross sections on the right were taken along ω₁(¹³C) from the 2D ¹³C,¹H COSY spectrum recorded with biomass that was harvested in the early stationary phase (see the text). Fifty-six and 44% of isoleucine are synthesized via the threonine and pyruvate pathways, respectively. The carbon chemical shifts are relative to those of DSS (2,2-dimethyl-2-silapentane-5-sulfonate sodium salt).