Isolation of a new member of the soybean Kunitz-type proteinase inhibitors

Proteinase inhibitors are present in almost all organisms. Most of these proteins are specific in their interaction with proteinases, inhibiting the proteolytic activity. In plants, this protein family is highly abundant in tubers of many species. Since high levels of proteinase inhibitor in agricultural crops may result in elevations of the digestive enzymes in human and animals, research has been targeted toward modification of the proteinase inhibitor levels in those plant species (Ryan, 1981). Soybean (Glycine max), among others, two important species of proteinase inhibitors have been characterized: The Kunitz inhibitor, which shows specificity for trypsin, and the Bowman-Rick, which inhibits trypsin, chymotrypsin, and elastase. During screening of a lambda gt11 cDNA library, we isolated a DNA-clone with an insert size of 802 bp.