Purification and partial characterization of Oenococcus oeni exoprotease

The exoprotease from Oenococcus oeni produced in stress conditions was puri fied to homogeneity in two steps, a 14-fold increase of specific activity a nd a 44% recovery of proteinase activity. The molecular mass was estimated to be 33.1 kDa by gel filtration and 17 kDa by sodium dodecyl sulfate-polya crylamide gel electrophoresis (SDS-PAGE). These results suggest that the en zyme is a dimer consisting of two identical subunits. Optimal conditions fo r activity on grape juice were 25 degrees C and a pH of 4.5. Incubation at 70 degrees C, 15 min, destroyed proteolytic activity. The SDS-PAGE profile shows that the enzyme was able to degrade the grape juice proteins at a sig nificantly high rate. The activity at low pH and pepstatin A inhibition ind icate that this enzyme is an aspartic protease. The protease activity incre ases at acidic pH suggesting that it could be involved in the wine elaborat ion. (C) 2000 Published by Elsevier Science B.V. All rights reserved.