A porcine lung SLPI WAP 2 fragment inhibits trypsin by sharing the preserved antielastase reactive site P1' Met 73 and P2' Leu 74

One acid stable trypsin inhibitor (around 16 kDa) was isolated from the porcine lung extract after clarification, acid precipitation and trypsin affinity chromatography. Its N-terminal sequence is MLNP. The polyclonal antibody against recombinant mouse secretory leukoproteinase inhibitor (SLPI) well recognized the inhibitor. The obtained N-terminal sequence corresponds to the antielastase reactive site P1' Met 73 and P2' Leu 74 and presents in SLPI WAP 2 domain. The reactive site was preserved active even after the inhibitor fragmentation that could occur during the trypsin affinity chromatography. The probable association of the 3.0 kDa SLPI WAP 2 fragment with GAG heparin (molecular mass around 14 kDa) responds to the molecular mass of the active inhibitor.