secondary metabolite biosynthesis polyketide biosynthesis UPa:UPA00473 GO:0030639 pathway PMID:8257119 Biosynthesis of polyketides, a large group of complex natural products produced mainly by species of Streptomyces and related filamentous bacteria that include antibacterial, antifungal, anticancer, antiparasitic and immunosuppressant compounds. Despite their structures being strikingly diverse, they share a common pattern of biosynthesis in which simple carboxylic acid units are condensed onto the growing chain by a polyketide synthase (PKS) in a process resembling fatty acid biosynthesis. PMID:2088174