Linking Peptide and Polyketide Biosynthesis.

ConclusionThe biosynthesis of natural products involves many similar reactions.In contrast to the art of the classical organic chemist, natural chemistry within living organisms operates with protein catalysts.These catalysts assemble the reactants and perform their tasks in general in neutral aqueous media at ambient temperatures.To perform the synthesis of a complex metabolite, the proteins mayhave to interact in various ways.The most simple is the reversible interaction of a set of proteins.More often, and especially in the formation of complex peptides, a covalent assembly ofenzymes has been found, poly-or multienzymes.This assembly seems at first sight to simplify complex processes.One protein may catalyse a complete set of reactions.It is not required to analyse each step of a multistep pathway in detail to finally be able to perform a multistep synthesis with manydifferent enzymes.One protein maytake up simple precursors, and deliver the final product, as all intermediates remain attached, just as in solid phase synthesis1^ During the past years many biosynthetic systems have been analysed in some detail, especially at the gene level.This analysis has brought many unexpected results.At the moment,weeven cannot fully appreciate the data, since most of it we cannot interpret.However, it tells us already manydetails of howthe biosynthesis of natural products is organized2).563