Characterization of inactive renin in mouse amniotic fluid

We have demonstrated high concentrations of inactive renin in mouse amniotic fluid compared with mouse plasma and other organs. Its molecular weight was similar to that of prorenin from the mouse submaxillary gland (42 000 daltons). The activated renin had a Km value of 1.48 greater than M which is identical to that of active amniotic fluid mouse renin. The time course and concentration dependence of trypsin activation was studied, and compared with activation by direct acidification and acidification by dialysis. The pH optimum for acid activation varied with temperature between pH 3 and 4, probably because of simultaneous activation and degradation. Acid activation was almost completely reversible.