Arthropod hemolymph contains proteins with serine proteinase inhibitory act
ivity. These inhibitors may exist in plasma or in hemocyte granules. Serine
proteinase inhibitors from the Kazal. Kunitz, alpha-macroglobulin, and ser
pin families have been identified in arthropod hemolymph and have been char
acterized biochemically. Two new families of low molecular weight serine pr
oteinase inhibitors have recently been discovered: one in silkworms (the Bo
mbyx family) and another in locusts and a crayfish. The serine proteinase i
nhibitors in arthropod hemolymph are likely to function in protecting their
hosts from infection by pathogens or parasites. Some may inhibit fungal or
bacterial proteinases. Others probably have roles in regulating endogenous
proteinases involved in coagulation, prophenol oxidase activation, or cyto
kine activation. (C) 1999 Elsevier Science Ltd. All rights reserved.