Protease

A protease is an enzyme that cuts other proteins into pieces. An enzyme is a protein that sets off a chemical reaction without being used up itself. A protease therefore works as a molecular pair of scissors, and can do so over and over again.

How does it work?

A protein is a chain of building blocks, the amino acids. The bond between two building blocks is very strong. Without help, such a bond stays intact in water for hundreds of years. A protease has a small cavity into which the protein it has to cut fits, and in that cavity are components that break the bond. This way the cutting takes place in a fraction of a second.

Proteases are selective. Most only cut at a particular spot in a particular protein, like scissors that can only cut one specific kind of thread.

Why it matters

Proteases do a lot of work in the body. In the intestines they cut food proteins into pieces the body can absorb. In cells they switch proteins on or off by cutting a piece off, and they clear away proteins that are no longer needed. Proteases also play a role in viruses: some viruses need one of their own to multiply. Medicines that inhibit such a protease therefore already exist.

Researchers also want to be able to design proteases themselves, for a protein of their choice. For example, the lab of Nobel laureate David Baker used AI to design enzymes that cut other proteins at a pre-chosen spot (link). In the test tube they cut, among other things, the protein that clumps together in Alzheimer's disease, and some also worked in living human cells. One pair of scissors can cut many targets in succession, which is a possible advantage over an antibody. This is research for now; many more steps are needed before it could become a medicine.