Activation and molecular weight changes of human plasma inactive renin by proteolytic enzymes

By treating human plasma with trypsin (1 mg/ml), 3 different peaks of renin activity were detected by a gel filtration on Ultrogel AcA 44. The molecular weights of these activated renins were estimated to be 47,000, 45,000 and 43,000 daltons, respectively. 2) The molecular weight of human plasma active renin partially purified was 43,000 daltons. After treatment with neuraminidase, the molecular weight decreased to 38,000 daltons. 3) When the partially purified plasma inactive renin, which was completely separated from active renin, was activated by trypsin, chymotrypsin, plasmin, pepsin and renin, the activated renins had different molecular weights. The highest molecular weight form (47,000-48,000) was trypsin-activated or plasmin-activated renin and the lowest molecular weight form (38,000) was renin-activated renin. 4) These results suggest that cleavage of the specific site in peptide bond of plasma inactive renin by various proteolytic enzymes results in different molecular weights of activated renins. Plasma active renin free from sialic acid is very similar to kidney renin.