EXOPROTEASE ACTIVITY OF LEUCONOSTOC-OENOS IN STRESS CONDITIONS

Exoprotease activity during 48 h of total energy and nutrient starvati on was examined in Leuconostoc oenos X2L isolated from wine. Starved c ells after 2 h of incubation at 30 degrees C in citrate buffer, 0.05 m mol l(-1) pH 5, showed greater extracellular proteolytic activity than at the onset of starvation. In the presence of 60 mg l(-1) SO2 and 8% or 12% ethanol, the proteolytic activity was higher; 10 mmol l(-1) Ca 2+ and Mg2+ produced an increase in protease activity during starvatio n. Glucose and 2-deoxyglucose (2-DOG) were found to repress synthesis by 80% and 100%, respectively. Cyclic adenosine 3'-5'-phosphate increa sed the exoprotease activity and reverted the repression by glucose an d 2-DOG. De novo synthesis of proteins was required for the exoproteas e activity by cells submitted to stress conditions. The absence of pro tease activity in the supernatant fluids from chloramphenicol-treated cells indicated that the activity is a result of deliberate release an d not of passive cell lysis.