Effects of linoleic acid and cations on the activity of a novel high-molecular weight protease, ingensin, from human placenta

1. 1. A linoleic acid-sensitive protease, ingensin, was purified to homogeneity from human placenta. The physical properties of the placental ingensin were found to be very similar to those of skeletal muscles ingensin [Ishiura et al. (1985) FEBS Lett. 189, 119–123]. 2. 2. The purified ingensin was activated by linoleic acid and SDS. The linoleic acid-activated form was inhibited preferentially by divalent cations, whereas the SDS-activated form was inhibited by monovalent cations instead.