Calcium-dependent protease in neuroblastoma cells

Extracts of neuroblastoma cells contained calcium-dependent proteolytic activity. This activity was accounted for by two distinct proteases. These proteases were separated by ion-exchange chromatography. Although each was totally dependent on calcium, the calcium requirements of the enzymes were different; one enzyme required approximately 40 microM Ca2+ for half-maximal activity and the other enzyme required approximately 150 microM Ca2+ for half-maximal activity.