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.