Identification of molting fluid carboxypeptidase A (MF-CPA) in Bombyx mori

Using microarray analyses, we identified carboxypeptidase A (MF-CPA), which was induced during pupal ecdysis in the wing discs of Bombyx mori. Here, we report the functional characterization of MF-CPA. MF-CPA has amino acid sequence similarities with the proteins in the carboxypeptidase A/B subfamily, from human to nematode. The MF-CPA gene is expressed during the molting periods in the epithelial tissues. MF-CPA is detected in the molting fluid, which fills the space between the old and new cuticle during molting. By Western blot analysis, we show that MF-CPA is secreted as a zymogen and processed in the molting fluid. Recombinant MF-CPA expressed in the insect cells has carboxypeptidase A activity. We propose that MF-CPA degrades the proteins from the old cuticle during the molting periods and contributes to recycling of the amino acids.