Enterocin, starter units

Fig. 34 Selection of novel wailupemycin 202—204 and enterocin analogs 205-207 generated by in vitro biosynthesis using unnatural starter units 199-201...

Type III polyketide synthases (PKSs) generate a diverse array of natural products by condensing multiple acetyl units from malonyl-CoA to specific starter substrates (1,2). The homodimeric enzymes orchestrate a series of acyltransferase, decarboxylation, condensation, cyclization, and aromatizatidn reactions at two functionally independent active sites. Due to their ability to vary either the starter molecule or the type of cyclization and the number of condensations, they are, along with terpene synthases, one of the major generators of carbon skeleton diversity in plant secondary metabolites (i). Among the starter substrates used, benzoyl-CoA is a rare starter molecule. It is utilized by bacterial type I PKSs to form soraphen A, enterocin and the wailupemycins (4). in plants, benzoyl-CoA is the starter unit for two type III PKSs, benzophenone synthase (BPS) and biphenyl synthase (BIS), both of which were cloned in our laboratory. 

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