A complex containing both trypsin inhibitor and dehydroascorbate reductaseactivities isolated from mitochondria of etiolated mung bean (Vigna radiata L. (Wilczek) cv. Tainan No. 5) seedlings

A complex containing trypsin inhibitor (TI) activity was extracted with 0.1 M TRIS buffer (pH 7.9) from trypsin-treated mitochondria of etiolated mung bean seedlings, and further purified with a Superdex 200 FPLC column. This partially purified complex with an M, about 820 kDa exhibited additional d ehydroascorbate (DHA) reductase activity with specific activities of 0.21, 1.53 and 1.54 mu mol ascorbate formed min(-1) mg(-1) protein at pH 6.0, 6.5 and 7.0, respectively, when glutathione was added, Much lower DHA reductas e activity (0.013 and 0.026 mu mol ascorbate formed min(-1) mg(-1) protein at pH 6.5 and 7.0, respectively) was found when glutathione was omitted. Th e isolated complex gave positive results when it was tested by ii activity staining after sos-PAGE, and could be recognized by a polyclonal antibody w hich was raised against 38 kDa sweet potato Kunitz-type TI, one of the root storage proteins of sweet potato. The possible physiological functions of this complex with both TI and DHA reductase activities were discussed.