The activity of a type II transmembrane serine protease, matriptase, is dependent solely on the catalytic domain.

Matriptase is a transmembrane serine protease comprising multiple domains in the extracellular region, including a stem domain and a catalytic domain. Using soluble matriptase variants containing entire extracellular domains or only the catalytic domain, the activity of this protease was found to depend solely on the catalytic domain. The stem domain had no significant effect on the activity.