Purification and characterization of α-chaconinase of Gibberella pulicaris

The potato pathogen Gibberella pulicaris (Fusarium sambucinum) is able to metabolize the potato saponin α-chaconine by first removing the 1,2-bound l-rhamnose. The catalyzing enzyme, α-chaconinase, is inducible by the substrate and α-solanine and α-tomatine. The protein with a molecular mass of about 95 kDa was purified by fractionated ammonium sulfate precipitation followed by concanavalin A-Sepharose chromatography and chromatofocusing. The enzyme is active over a wide pH and temperature range and is highly substrate specific for α-chaconine with a Km value of 0.97 mM and Vmax of 37.13 nkat. α-Solanine and α-tomatine are not converted by the enzyme.