I am using XOD in one of my reagents (EDTA + a stock buffer of KH2PO4 and Na2B4O7-10H2O; pH 8.2) for superoxide dismutase enzyme kinetic assays. Since XOD is sold in units, I am going to reconstitute all of my XOD at once and am looking to then aliquot and freeze my slurry at -20 to -80 C. Sigma recommends keeping the lyophilized XOD between 2-8C, though I am unsure whether freezing my aliquots at -20 to -80C and then thawing them would compromise enzyme quality. I am also concerned about how long XOD lasts in the freezer. Other products, such as superoxide dismutase, last up to 2 years after aliquoting and freezing at -20C. Thanks for any help or insight you may have to lend.
It shall be stable. Avoid repeated freezing and thawing by preparing multiple aliquots.
Dear James Murphy,
The activity of enzyme will decrease if it is always freezing and thawing. So, its better to store your enzyme in 5% glycerol so that you can store your aliquots in -20 to -80 for long time . The activity of enzyme wont decrease as compared to storing enzyme with out glycerol.
All the best.
Thank you for your feedback, Raghu and Ramesh. Upon aliquoting and freezing my XOD dilutions, I think I will keep them for about a year at -20C before remaking the stock. I was also able to obtain Sigma's protocol for testing enzyme viability, though they have not looked into enzyme stability over time. I'll be looking into this in the future.
Best,
James
Hello,
I'm a new PhD student and I had the same question about frozen xanthine oxidase solution stability.
May I ask you in which paper you saw that 5%glycerol enhances the stability? cause I can't find it in the litterature!;p
Thank you for your help.
Samantha
Dear Samantha,
Once go through this paper in this they have used 30% of glycerol but it has some side Effects on the enzyme function. But we optimized 5 % where it works good. All the best.
http://www.ncbi.nlm.nih.gov/pubmed/4341691
Thank you for your answer!
I will do it in that way and check the activity.
Best,
Samantha
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