ISOLATION AND ALPHA-AMIDATION OF THE NON-AMIDATED FORM OF CECROPIN-D FROM LARVAE OF BOMBYX-MORI

Two forms of cecropin D, an antibacterial protein, were isolated from larvae of the silkworm, Bombyx mori, immunized with Escherichia coli. One was the mature form and the other seemed to contain a glycine residue at its C-terminus. The latter was converted into the mature form in vitro by peptidylglycine alpha-amidating enzymes from horse serum and the result clearly demonstrates that this protein is the precursor of cecropin D. The mature form had 4- to 5-fold higher antibacterial activity against E. coli or Acinetobacter sp., suggesting that the amidation is important for full expression of antibacterial activity.