Isobutyrate as a precursor of n-butyrate in the biosynthesis of tylosine and fatty acids.

Labelled sodium isobutyrate [(CD3)2-CHCOONa] was added to the culture medium of Streptomyces fradiae and up to 14 atoms of deuterium were found to be incorporated into a molecule of tylosin aglycone (tylactone). This observation is in accordance with the data in the literature. When fatty acids were analyzed, as much as 34% of the isobutyrate incorporated into the cell was formed to be transformed into butyrate that was used for the synthesis of even, straight-chain fatty acids; 57% of the labelled isobutyrate was incorporated into the even isoacids, whereas 9% was degraded to propionate and further used for the synthesis of the odd acids.