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

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 muscle ingensin Ishiura et al. (1985) FEBS Lett. 189, 119-123]. 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.