Slow migrating proteinase inhibitors in human urine.

By means of a sensitive electrophoretic technique for the detection of proteinase inhibitors three slowly migrating proteinase inhibitors (SMPI) were discovered in some samples of pathological urine. SMPI 1 migrated in the beta 2-zone whereas SMPI 2 and SMPI 3 appeared in the anodal and cathodal gamma-zone, respectively. Only SMPI 1 and 2 were examined in detail. These were found to inhibit tryptic and elastolytic digestion, but not chymotryptic or plasminolytic digestion of casein. Immunological investigations revealed no similarity to normally occurring proteinase inhibitors in serum and urine. The SMPIs from one sample of urine were partially purified by DEAE-Sephadex ion exchange chromatography, followed by gel filtration on Sephacryl superfine 200. This procedure did not separate the two inhibitors. The molecular masses were estimated to be 25 000 Da by gel filtration, and 23000-26500 Da by SDS polyacrylamide gel electrophoresis.