Incorporation of amino acid-derived carbon into tylactone by Streptomyces fradiae GS14

Washed cells from 72-h cultures of Streptomyces fradiae GS14 were used to examine the distribution of radiolabel from 14C-amino acids and related compounds into tylactone, CO2, and cells. Test compounds were categorized according to products of their oxidative degradation. Those compounds known to produce propionyl-coenzyme A by direct catabolic oxidation were designated as group I. Group II included those compounds oxidized to methylmalonyl-coenzyme A via succinyl-coenzyme A and the tricarboxylic acid cycle. Group III contained compounds known to be oxidized to acetoacetyl-coenzyme A. The total amount of label recovered after 60 min ranged from 3 to 65%. Although label from all test compounds except proline (group II) and lysine (group III) was incorporated into tylactone after 60 min, label from group I and group III compounds was incorporated at levels five times greater than label from group II compounds. From 55 to 75% of the recovered label from propionate (I), asparagine (II), glutamine (II), glutamate (II), alpha-ketoglutarate (II), and succinate (II) was recovered as 14CO2. From 75 to 95% of the recovered label from the remaining compounds tested was located in the cells. Based on the data, a pathway for the role of amino acids in the biosynthesis of tylactone is proposed.