Insect inhibitors of metalloproteinases

Two types of peptidic metalloproteinase inhibitors have recently been identified in insects. A homologue of vertebrate tissue inhibitors of metalloproteinases (TIMPs) was found in the fruitfly Drosophila melanogaster which may contributes to regulation of a corresponding matrix metalloproteinase (MMP). The first member of MMPs from insects which shares similarity with vertebrate MMPs has also been cloned and characterized from Drosophila, suggesting conserved evolution of both MMPs and TIMPs. The first insect inhibitor of metalloproteinases (IMPI), which was identified in larvae of the greater wax moth, Galleria mellonella, shares no sequence similarity with known vertebrate or invertebrate proteins and represents the first non-TIMP-like inhibitor of metalloproteinases reported to date. In contrast to TIMPs, the IMPI is not active against MMP's but inhibits microbial metalloproteinases such as bacterial thermolysin. Insects may recognize such toxic metalloproteinases associated with invading pathogens by particular peptidic fragments that result from their nonregulated activity within the hemolymph. Metalloproteinases induce expression of the IMPI along with other antimicrobial proteins in course of humoral immune response of G. mellonella, thereby mediating regulation of metalloproteinase activity released within the hemolymph and inhibition of pathogen development as well.