Some important peptides of bacterial or fungal origin are synthesized via a template-directed, nucleic-acid-independent nonribosomal mechanism. Recent studies revealed that there is a special kind of macroenzymes, nonribosomal peptide synthetases, which plays a key role in the alternative system. Nonribosomal peptide synthetases are composed of modules, the sequences of which contain the message for peptide synthesis. The understanding of the structure and function of nonribosomal peptide synthetases enables scientists believe that some new peptides can be produced by modifying or recombining these special enzymes.