Expression of the Arrowhead Proteinase Inhibitor B (API) Gene in the Silkworm Larvae and Pupae

The arrowhead proteinase inhibitor B (API) gene was cloned into baculovirus transfer vectors of pBacPAK8 and pOSX, and two recombinant transfer vectors, pBacPAK (API) and pOSX (API), were constructed. Co-infection was accomplished with either one of the recombinant transfer vectors and Bm-BacPAK6 DNA in BmN cells. Then recombinant virus of CrBK9, CrBK10 and BX was selected. API gene was successfully expressed in silkworm larvae and pupae. The recombinant API (rAPI) showed strong inhibitive activity on bovine pancreas trypsin. The inhibiting activity of the expression product was 1.0x10(5) u/ml haemolymph for silkworm larvae and 1.3x10(5)u/ml haemolymph for pupae. In addition, SDS-PAGE of the preliminarily purified rAPI showed its molecular weight to be about 19 kD.