A mutant generated by expression of an engineered DEBS 1 protein from the erythromycin-producing polyketide synthase (PKS) in Streptomyces coelicolor produces the triketide as a lactone, but the major product is the nor-analogue derived from acetate as starter acid

Genetic engineering of theerythromycin polyketide synthase (PKS), to generate the DEBS 1 protein with a fused thioesterase domain (DEBS 1-TE), followed by expression in Streptomyces coelicolor, resulted in a mutant which produces a small quantity of the erythromycin triketide as a lactone, but the major product is the corresponding nor-analogue derived from acetate rather than propionate as the starter acid.