The activity of plasmin and plasminogen is expressed in CU. What is this, and what is the equivalent in nkat?

CU stands for Casein Units, and is a measure of the proteolytic activity on the substrate casein. For example, a plasminogen reagent when activated to plasmin with streptokinase can show an activity of 7.3 nkat (S-2251™) per CU. 1 mg of plasmin corresponds to 0.20 nkat (S-2251™), or to 0.024 CU.