By shifting evolution into reverse, it may be possible to use “green chemistry” to make a number of costly synthetic drugs as easily and cheaply as brewing beer. Normally, both evolution and synthetic chemistry proceed from the simple to the complex. Small molecules are combined and modified to make larger and more complex molecules that perform specific functions. Bioretrosynthesis works in the opposite direction. It starts with the final, desired product and then uses natural selection to produce a series of specialized enzymes that can make the final product out of a chain of chemical reactions that begin with simple, commonly available compounds.
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