Flow as a regulator of the activation of factor X by tissue factor.

A novel enzyme reactor for phospholipid-dependent reactions was used to study the effects of flow on tissue factor-initiated coagulation. Microcapillaries were coated with a phospholipid bilayer containing tissue factor, a transmembrane protein that is an essential cofactor for a plasma procoagulant enzyme, factor VII. We show that, in contrast to static, closed systems, the steady-state catalytic activity is independent of enzyme concentration and the time to steady state becomes a function of the enzyme concentration.