CHANGES OF A RICE DEBRANCHING ENZYME DURING SEED FORMATION AND GERMINATION

A starch debranching enzyme was purified from rice seeds to be homogeneous in molecular mass and used to raise antiserum. This antiserum reacted specifically with a debranching enzyme isolated from rice seeds, but did not react with those from potato tuber, barley seed or Klebsiella cells. Rice seeds were collected during seed formation and germination, and extracted proteins were analyzed by immunostaining following electrophoresis. The concentration of this enzyme protein estimated by immunostaining was maximal at the mid-maturation stage and was essentially constant during the late-maturation stage; this was contradictory to a decrease in activity. In dry seeds there was little debranching enzyme present in the soluble protein fraction, but there was a rapid increase of it during germination associated with an increase in its activity and a slight change of isoelectric point. The enzyme present in the total protein fraction showed maximum accumulation during the early stage of germination but decreased slightly later. These quantitative results suggest that the latent form of debranching enzyme was converted into an active form during seed germination. © 1991, Gustav Fischer Verlag, Stuttgart. All rights reserved.