Stability of CYP activity in Bactosomes after repeated freeze-thawing

Procedure
Bactosomes were subjected to a given number of freeze-thaw cycles, consisting of a gentle thawing on ice, followed by a rapid re-freezing on dry ice. Residual CYP activity was then measured, using Cypex's standard test substrates.

Results
The results are presented in the following graph as the residual CYP activity (expressed as a percentage of control activity) remaining after the indicated number of freeze-thaw cycles.

Results are expressed as mean ± SD, n=3, except where indicated (*), where n=2 (mean ± range).
Activities measured were as follows: CYP3A4, testosterone 6b-hydroxylase; CYP1A2, 7-ethoxycoumarin O-deethylase; CYP2D6 dextromethorphan O-demethylase; CYP2C19 diazepam N-demethylase; CYP2C9, diclofenac 4'-hydroxylase.

Conclusions
CYPs 1A2 and 3A4 appear to be relatively refractory to the effects of multiple freeze-thawing. CYPs 2D6, 2C19 and 2C9 show a decrease in activity, although the effect is small (10-20% decrease after 5 cycles).

Made under licence from BTG International Ltd (AU730155, EP0914446, US6566108 and other patents pending).

United States Patent Nos. 5,420,027 or 5,240,831, Canada Patent No. 2100245 and other patents pending.