PURIFICATION AND CIRCULAR-DICHROISM STUDIES OF MULTIPLE FORMS OF ACTINIDIN FROM ACTINIDIA-CHINENSIS (KIWIFRUIT)

Actinidin, a cysteine proteinase from the kiwifruit (Actinidia chinens is), is composed of multiple forms. By means of anion-exchange high-re solution liquid chromatography four actinidin isoforms were isolated a s homogeneous proteins with molecular weights of 27 kDa. These enzymes possess similarities in secondary structure, as indicated by their ci rcular dichroism (CD) spectra in the far-ultraviolet region (185-250 n m), which gave results in good agreement with those derived from previ ous X-ray diffraction studies of actinidin. The CD curves of the actin idin forms lacked the shoulder at 200 nm which is characteristic of pa pain and proteinase Omega spectra. Since the molecular structures of t he three proteinases mentioned above are very similar, it is likely th at spectral differences among them originate from aromatic side-chain contributions.