Purification of a trypsin inhibitor secreted by embryogenic carrot cells

A protease inhibitor with a molecular weight of about 12,800 was purified to electrophoretic homogeneity from Daucus carota cells. The protease inhibitor was heat stable and inhibited trypsin but had no activity toward chymotrypsin or subtilisin. Nonembryogenic as well as embryogenic strains contained the inhibitor in similar amounts, but in the embryogenic strains the trypsin inhibitor was released from the cells and as a result accumulated in high concentrations in the culture medium, whereas no release of the trypsin inhibitor was found during cultivation of the nonembryogenic strains. Very low amounts of acid phosphatase or α-mannosidase activity were found in the culture filtrate of both embryogenic and nonembryogenic strains, which suggest that the release of the inhibitor from embryogenic strains was not due to cell lysis.