Serine Peptidase Inhibitor Kunitz Type 3 (SPINT3)

SPINT3, Contains 1 BPTI/Kunitz inhibitor domain. Proteins from the Kunitz family contain from 170 to 200 amino acid residues and one or two intra-chain disulfide bonds. The best conserved region is found in their N-terminal section. The crystal structures of soybean trypsin inhibitor (STI), trypsin inhibitor DE-3 from the Kaffir tree Erythrina caffra (ETI) and the bifunctional proteinase K/alpha-amylase inhibitor from wheat (PK13) have been solved, showing them to share the same 12-stranded beta sheet structure as those of interleukin 1 and heparin-binding growth factors. The beta-sheets are arranged in 3 similar lobes around a central axis, 6 strands forming an anti-parallel beta barrel. Despite the structural similarity, STI shows no interleukin-1 bioactivity, presumably as a result of their primary sequence disparities.