A. Mostafaie, M. Chalabi,
Volume 10, Issue 3 (10-2006)
Abstract
Proteolytic enzymes play important roles in food and drug industries. Actinidin, the most abundant protein of kiwifruit is a cystein protease (EC 3.4.22.14). In the present study, protein contents and levels of actinidin in kiwifruit cultivars were assayed and the enzyme was purified by a simple procedure. Actinidin was purified using two steps: (1)) precipitation by ammonium sulfate and (2) ion-exchange chromatography on diethylaminoethyl Sepharose. Molecular mass and proteolytic activity of the purified enzyme were determined by SDS-PAGE and casein digestion test, respectively. Protein content of the cultivars was compared by three different methods, namely, Bradford, UV and Lowry methods. The yield and degree of enzyme purity were 65 and 95 percents, respectively. Molecular mass of the purified enzymes were estimated 29 KDa in reducing SDS-PAGE. Results of the protein assays showed that protein and actinidin contents of kiwifruit were overestimated using UV or Lowry methods for assay. It was concluded that Bradford method is more accurate than UV or Lowry methods for measurement of protein level in kiwifruit.
