What is "pacifastin"

Pacifastin is a family of serine proteinase inhibitors found in arthropods. Pacifastin inhibits the serine peptidases trypsin and chymotrypsin.

All pacifastin members that have been characterized at the molecular level are precursor peptides composed of an N-terminal signal sequence followed by a precursor domain and a variable number of inhibitor domains. Each of these inhibitor domains carries a six-cysteine motif - see below.

The first family members to be identified were isolated from Locusta migratoria migratoria(migratory locust) which were HI, LMCI-1 (PMP-D2) and LMCI-2 (PMP-C). A further five members, SGPI-1 to 5, were then isolated from Schistocerca gregaria (desert locust), and a heterodimeric serine protease inhibitor was isolated from the haemolymph of Pacifastacus leniusculus (Signal crayfish), and named pacifastin.