Fig. 2. Characterization of the biosynthetic origin of TXNs by precursor feeding experiments. (A) Summary of feeding results with 13C-labeled sodium acetate and 13C6-l-isoleucine (Ile). (B) MS analysis of production of TXN by fermentation without (I) or with 13C6-l-Ile (II). (C) 13C-NMR spectra of TXN-A with (II) and without (I) feeding of 13C6-l-Ile. The enhanced signals of C-13, C-14, C15, C-16, and C-17 are marked. (D) The enlarged parts of 13C-NMR spectra from feeding experiment.
