Purification and characterization of tomato polygalacturonase converter

Abstract

Extracts of ripe tomatoes contain 2 forms of polygalacturonase (PG I and PG II). A heat-stable component that binds PG II to produce PG I was isolated from tomato fruit. This component was named polygalacturonase converter (PG converter). The PG converter was purified by gel filtration, ion-exchange chromatography and chromatofocusing. It appears to be a protein with a relative molecular mass of 102,000. It was readily inactivated by papain and pronase. The converter was labile at alkaline conditions, and treatment of PG I at pH 11 released free PG II. A similar factor with a low molecular mass was extracted from tomato foliage.