OBSOLETE. Catalysis of the cleavage of N-terminal leader sequences from membrane prolipoproteins. Hydrolyzes the terminal bond of Xaa-Xbb-Xbb-Cys, in which Xaa is hydrophobic (preferably Leu), Xbb is often Ser or Ala, Xcc is often Gly or Ala, and the Cys is alkylated on sulfur with a diacylglyceryl group.