A Classification of Modular Enzymes

A modular architecture is no particular hallmark of enzymes, the highest degree of modularity is typically observed in structural proteins of the extracellular matrix and in proteins involved in intracellular signal transduction. Nevertheless, there are a number of modular enzymes including some which are of interest for biocatalytic applications. 

The third type of modularity, the multi-catalytic enzymes using substrate channelling, are of particular interest for synthetic applications. Prominent members are the fatty acid synthases, the polyketide synthases and the non-ribosomal peptide synthases l42-44 . in these large proteins, a number of catalytic domains is combined with accessory domains and allows the catalysis of an entire pathway by a single polypeptide chain. Multi-catalytic enzymes frequently use a swinging arm , which is covalently attached to the intermediary product of one reaction step, and is subsequently able to present this molecule to the next catalytic domain for further 

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