A high molecular weight form of human urinary urokinase.

A very high molecular weight form of urokinase, of about 100,000 D (VHMr-UK), was isolated from human urine in trace amounts as compared to the well characterized two forms of urokinase, HMr-UK (Mr of about 50,000) and LMr-UK (Mr of about 30,000). This form was demonstrated to be a dimer of HMr-UK, in which no covalent bond is involved, on the basis of the following evidence: by SDS electrophoresis it is dissociated, to the 50,000 D form; by electrophoresis in SDS under reducing conditions it is dissociated, as HMr-UK, to two polypeptide chains of about 30,000 and 20,000 D; by short heating at pH 5 it is quantitatively converted to the 50,000 D form; the kinetic constants towards the alpha-carbobenzoxy-L-lysine-p-nitro-phenylester substrate are the same for HMr-UK and VHMr-UK.