Term coined by Constance Jeffery at Brandeis University for multifunctional enzymes, proteins which have many different functions.

As the sequences of complete genomes become available, the new challenge in biology is to assign functions to all the proteins whose sequence is known. We are now beginning to learn that there is not always a 1 to 1 correspondence between a protein and a function. Some proteins assemble with several others to carry out a function (see quaternary structure, modulator protein) and some proteins have multiple functions. The second class of proteins are known as multifunctional enzymes or moonlighting proteins.


The function of a moonlighting protein can vary as a consequence of many things. Some factors include ...


The evolution of moonlighting proteins raises two questions - (1) How did moonlighting proteins evolve? and (2) What is the advantage to having several functions on one protein?

The most straightforward answer is that organisms make use of what is already available. Many of the moonlighting enzymes are ones that are ubiquitously available in the cell, e.g. metabolic enzymes. If a new function is required, it is more likely that an existing enzyme will adapt to a new function rather than a new enzyme created de novo to accomodate this function. Glycolitic enzymes have been around since the earliest bacteria and ample time has passed to build these proteins into other cellular processes.

The advantage of moonlighting enzymes is straightforward ... the organism has to manufacture fewer proteins when one protein carries out several functions. This means less materials consumed to make proteins, and less energy spent replicating DNA. This could save a great deal of energy during growth and replication.

see also evolution of metabolic pathways