Chymotrypsin-like serine proteinases are involved in the maintenance of cell viability

► Novel chymotrypsin-like activity implicated in the maintenance of cell viability. ► Inhibition by TMR-PheP(OPh)2 caused a decrease in HeLa and U251 cell viability. ► Reduced viability was associated with an increase in caspase-3 activity over time. ► PARP cleavage and phosphatidylserine translocation were also observed. ► Inhibition of this protease initiates a cascade of apoptotic-related events.