Everyone had thought that only special chemical scissors, strips of protein called enzymes, could snip out the junk.

Feathers have similar keratins and are extremely resistant to protein digestive enzymes.

Before these discoveries, it was believed that biological catalysis was solely the realm of protein enzymes.

At the same time some of the cells' protein enzymes were cleaved and inactivated.

On earth, organisms had evolved by learning to carry out biochemical reactions in a small space, with the help of protein enzymes.

What has made the difference is adding a third drug, usually one that attacks a different viral enzyme, a protein enzyme known as protease.

Most catalysis in cells is carried out by protein enzymes.

Phosphorylation turns many protein enzymes on and off, thereby altering their function and activity.

These reactions are often catalyzed by protein enzymes.

Biocatalysis is the use of natural catalysts, such as protein enzymes, to perform chemical transformations on organic compounds.