Modular enzymes.

Although modular macromolecular devices are encountered frequently in a variety of biological situations, their occurrence in biocatalysis has not been widely appreciated. Three general classes of modular biocatalysts can be identified: enzymes in which catalysis and substrate specificity are separable, multisubstrate enzymes in which binding sites for individual substrates are modular, and multienzyme systems that can catalyse programmable metabolic pathways. In the postgenomic era, the discovery of such systems can be expected to have a significant impact on the role of enzymes in synthetic and process chemistry.