Frequently Asked Questions
Click the question below to expand and view the answer.
» Back to All FAQ Categories
S9 and Cytosol
Do you have S9 and cytosol fractions that correspond to the microsomal products?
Yes, please contact us to help you find the corresponding subcellular fractions. Availability may be limited.
What is the difference in CYP activities between human liver microsomes and human liver S9?
Microsomes are derived from S9 by a centrifugation process which separates the microsomal fraction of S9 from the cytosol, concentrating the CYP enzymes in the microsomal pellet. As a consequence, CYP activities in the microsomal fraction are approximately four to five times greater than that of its parent S9 fraction.
Why are the activities in your average pool of human liver microsomes generally higher than another commercially-available "high activity" pool?
We are confident that the activities in our pooled human liver microsomes reflect a true average range--not high activities.
Our acceptance criteria are calculated from our historical data, which represents the characterization of over 400 individual human livers to date. We select each of the 50 donors that comprise this pool and combine them to ensure that average activities are met for each of the enzymes, and that each donor is significantly represented in the pool.
All of our enzymatic assays are performed using LC/MS/MS validated methods, and all data are reviewed by our Quality Control staff prior to the product's release, so we are confident that the product you receive reflects average human activities.