The invention relates to a recombinant kunitz
protein of third-generation
botryosphaeria formosa as well as a preparation method and application of the recombinant kunitz
protein, and belongs to the technical field of fish parasite
protein expression and
function application research. The
serine protease inhibitor of the third-generation
botryosphaeria formosa is a GcKSI protein, and the
amino acid sequence of the GcKSI protein is as shown in SEQ ID NO: 2. According to the invention, the
amino acid sequence of the GcKSI protein is optimized, and the GcKSI recombinant protein rGcKSI is obtained through
prokaryotic expression. The rGcKSI inhibits
complement activity of host fish
in vitro and has an obvious inhibition effect on
serine protease, after injection immunization of the rGcKSI and third-generation
insect infection experiments, the
infection rate and the average infection intensity of the rGcKSI are obviously lower than those of a control group, and it is proved that the rGcKSI has good immunoprotectiveness on third-generation
insect infection, and the rGcKSI can be used as an
immunopotentiator for the third-generation
insect infection of the
tilapia. The GcKSI
gene of the
serine protease inhibitor and the GcKSI protein coded by the GcKSI
gene can be used as new targets for
drug research and development.