Isolation of urokinase by affinity ultrafiltration

A water‐soluble, ligand‐bound polymer has been synthesized for the purpose of isolation of urokinase, an important plasminogen activator. The affinity polymer was formed by copolymerizing N‐acryloyl‐m‐aminobenza‐midine and acrylamide in the absence of oxygen. An affinity ultrafiltration process was then developed for isolating urokinase from an artificial solution containing peroxidase and urokinase and from a crude urine source. The process yields were determined to be 86% and 49%, respectively. The recovered urokinase exhibited a specfic activity close to that of the highest commercial grade. This article also presents a new technique for assaying urokinase by coupling plasminogen with L‐benzoyl arginine‐p‐nitroanilide (L‐BAPNA), an inexpensive chromogenic substrate.