Structure of biocatalysts depends on whether they are in cells or test tubes

The structure of enzymes determines how they control vital processes such as digestion or immune response. This is because the protein compounds are not rigid, but can change their shape through movable 'hinges.' The shape of enzymes can depend on whether their structure is measured in the test tube or in the living cell. This is what physicochemists discovered about YopO, an enzyme of the plague pathogen.

from Health & Medicine News -- ScienceDaily https://www.sciencedaily.com/releases/2020/04/200424132558.htm