Building-block selectivity of polyketide synthases.

For the past decade, polyketide synthases have presented an exciting paradigm for the controlled manipulation of complex natural product structure. These multifunctional enzymes catalyze the biosynthesis of polyketide natural products by stepwise condensation and modification of metabolically derived building blocks. In particular, regioselective modification of polyketide structure is possible by alterations in either intracellular acyl-CoA pools or, more commonly, by manipulation of acyl transferases that act as the primary gatekeepers for building blocks.