Chymotrypsin and trypsin inhibitor isolated from potato tubers

Potato Kunitz-type chymotrypsin inhibitor (PKCI-23) was isolated from potato tubers (Solanum tuberosum L., cv. Zhukov’s Jubilee) and purified to a homogenous state. The protein was purified by gel-filtration chromatography and ion-exchange chromatography using Sephadex G-75 and CM-sepharose CL-6B, respectively. PKCI-23 protein has been shown to inhibit both chymotrypsin and trypsin with equal efficacy, forming equimolar complexes with these enzymes. However, much weaker inhibitory effect of PKCI-23 has been observed for subtilisin Carlsberg. The N-terminal 20 amino acid sequence of PKCI-23 has been sequenced. PKCI-23 has been shown to suppress, with different efficacy, the growth and development of pathogenic microorganisms Fusarium culmorum (Wm. G. Sm.) Sacc. and Phytophtora infestans (Mont.) de Bary that infect potato.