How should I store my protease?

This product is stable for at least 4 years from date of manufacture if stored unopened between -15 to – 25°C. Internal studies have shown the reconstituted enzyme is stable as a frozen solution between -15 to – 25°C for at least 6 months without loss of potency. Additional internal studies have shown the enzyme can go through a freeze-thaw cycle at least once without loss of potency by neutral protease (NP) assay.