Abstract
Three different types of proteinase inhibitors, I, II and III, were fractionated from Japanese radish seed by repeated column chromatographies on SE- and CM-cellulose. The finally purified preparation of inhibitor III was found to be homogeneous by both chroma-tographic and electrophoretic analyses. All three of them strongly and stoichiometrically inhibited trypsin whereas they showed weak inhibition on other proteinases, such as chymotrypsin, Nagarse and Pronase. From nitrogen content and ultraviolet absorption spectra, each of the inhibitors I and III .vas confirmed to be a protein. The molecular weights of inhibitors I and III were calculated to be 8000 and 12, 000, respectively. These inhibitors were stable at temperatures above 90°C in an acidic pH.
