Purification and partial amino acid sequence of initiatorin, a prostatic endopeptidase of the silkworm, Bombyx mori

Abstract We have purified initiatorin, a prostatic endopeptidase that initiates the protein-arginine degradation cascade in the spermatophore of Bombyx mori . Purification of the enzyme from spermatophores was monitored by measuring BAEE (Nα-benzoyl- l -arginine-ethyl ester) hydrolyzing activity. Spermatophores were used as a source for this enzyme. Of several isoforms the major form (MW, 29 kDa) was purified over 200-fold. The N-terminal sequence of initiatorin showed strong homology with those of serine-type of endopeptidases.