How a flexible enzyme found a new target
Nylon is a human-made plastic, so a bacterium that can use nylon waste as food raises an obvious question: where did the ability come from? The key may not be a wholly new kind of chemistry. Some enzymes—proteins that speed up chemical reactions—can act on more than one molecule when their active site, the pocket where a molecule binds, is a little flexible.
That flexibility can let an enzyme accommodate a molecule it was not originally specialized for. If the fit is close enough, the enzyme may also break a chemical bond in that molecule. In this case, a modest change in fit could allow an enzyme that acts on other compounds to bind and break bonds in nylon-manufacturing waste.
A small change can matter
An enzyme’s shape helps determine which molecules it can work on. A slight alteration can change how well a target sits in the active site, much as a small adjustment to a tool can make it grip a different fastener. The underlying reaction need not be entirely new: the altered fit can extend chemistry the enzyme could already perform to a new material.
Once nylon-derived compounds are broken into smaller pieces, a bacterium may be able to take them up and use them. That does not mean the plastic disappears instantly or that every nylon item is readily digestible. The ability described here concerns nylon-manufacturing waste and depends on the relevant enzyme acting on its bonds.
Evolution’s opportunistic route
This is one way biological innovation can arise: an existing protein with a somewhat permissive shape gains a useful new target through a small change. For a bacterium living where nylon-related compounds are available, that extra activity could provide access to a food source that was absent before nylon existed. A modern material, in other words, may be met not by brand-new chemistry, but by an old molecular tool whose fit has shifted.
