Tetracyclines are aromatic polyketide antibiotics produced by Streptomyces species via type II polyketide synthases (PKSs). Tetracyclines contain a linear tetracyclic skeleton, which is formed from a malonamate starter unit and malonyl-CoA extender units through a common polyketide pathway [MD:
M00778]. This diagram shows biosynthesis of naturally occurring tetracyclines (tetracycline, oxytetracycline and chlortetracycline) via a common intermediate anhydrotetracycline [MD:
M00780 M00823].