Amino acid sequences of the two smallest trypsin inhibitors from sponge gourd seeds.

Sponge gourd (Luffa cylindricd) seeds contain several biologically active proteins. Recently, we found that the mature seeds contain three types of trypsin inhibitors having molecular masses of about 13 kDa (type I), 6.5 kDa (type II), and 3.2 kDa (type III). Furthermore, preliminary experiments suggested that the type III one might be a domain unit of these inhibitors. Here, we present the isolation and the amino acid sequences of two isoforms of type III trypsin inhibitors. The inhibitors were extracted from the defatted meal of sponge gourd seeds purchased from Takii Co. with aqueous 10% NaCl solution adjusted to pH 4.0 with HC1, and precipitated with ammoniumsulfate between 50% and 100%saturation. After the precipitate was dissolved and dialyzed against 10mM Tris-HCl buffer (pH 8.5), the