How long can I store microsomes and S9?
These products should always be stored in an ultracold freezer at temperatures < -70° C. Stored under these conditions the cytochrome P450 enzyme systems are remarkably stable, showing little, if any, loss of activity after storage for more than 5 years. However, some of the phase II enzyme systems, particularly those in S9 such as N-acetyltransferase, are not stable even at -70° C, and lose significant activity within a matter of weeks or months.
