[A high-molecular-weight protease, ingensin, from human placental chorionic tissue--purification and studies of...

Recently, the identification of several proteases of nonlysosomal origin has been reported. In this study, a high-molecular-weight protease, ingensin, was purified from human placenta, and the biological and physiological properties of this enzyme were investigated. The activity of ingensin was determined with a synthetic substrate, succinyl-leucyl-leucyl-valyl-tyrosine-methylcoumarinamide (SLLVT-MCA). The molecular weight of ingensin was calculated to be about 700,000 by HPLC gel filtration. Ingensin was separated into a major subunit of 70,000 and minor subunits of 105,000 and about 30,000, respectively, under the denaturating conditions. Maximum ingensin activity was observed in the presence of 0.06 to 0.08% sodium dodecyl sulfate (SDS). Ingensin was activated by linoleic acid and arachidonic acid. A subcellular fractionation study suggested that there was a large amount of ingensin activity in the microsome or cytosol fraction. An indirect immunofluorescent study showed that ingensin was localized in the trophoblast cell layer and epithelium of the vessel interstitial tissue. Ingensin hydrolyzed several proteins in human placental tissue, and had liberated ALP from the placental membrane. These results indicated that a new protease, ingensin, may be involved in protein turnover in placental tissue.