Do I have to supplement the purified collagenase with a protease source?

Yes. 

VitaCyte’s collagenase products are chromatographically purified to minimize contamination of protease. Collagenase with negligible protease contamination ensures minimal loss of collagen degradation activity during storage or as a frozen solution. Purified collagenase alone is ineffective in releasing cells from tissue since protease activity is required to degrade other extracellular matrix proteins (see Mechanism FAQs). Therefore, the selection of an appropriate protease used at an optimal dose is likely the most important decision a cell isolator can make to ensure recovery of an adequate amount of functional cells.