Author contributions
VFL and DMD designed the experiment. VFL, FBSF, NPP and SACS performed the 13C-labelling experiment. Mass spectrometry analysis was performed by DBM under the supervision of ARF. Data analysis was performed by VFL, FBSF, SACS, AE, JK and DMD. All authors contributed to write the final manuscript. DMD obtained funding and is responsible for this article.