We have performed assays when lipase was exposed to repeated freezing-thawing cycles in presence of some cryoprotectants and we observed interesting phenomenon. When trehalose was used as protectant, enzyme activity during initial cycles exceeded the activity before freezing. Does anyone has an idea how is that possible?
Hi Stanislav,
I do remember directly related to your question old publication in CRYOBIOLOGY, volume 29, issue 2, pages 281-290 (1992), entitled “Effect of freezing-thawing on invertase activity”. Dr. Marli Breda et al. have studied the effect of freezing-thawing on invertase activity (v0) by varying the following parameters: chemical nature of the buffer, pH (4.0 to 9.0), and freezing rate (instantaneous (liquid N2), 300, 90, and 33 °C/h). The cryoprotection capability of polyols at 10 g/liter concentration was also determined (glycerol, ethylene glycol, propylene glycol, and PEG 400). After thawing, it was observed that a variation in v0 more or less ACCENTUATED all parameters cited. Among polyols, PEG 400 was found the most efficient cryoprotectant.
Best wishes,
Ilya
I did come across this phenomenon 25 years ago in discussion with a research group in Estonia. But I never discovered whether it was some artefact or real. It is known that an enzyme can have multiple conformational states depending upon the environment, particularly water activity, so it is theoretically possible that the freeze-thaw (reduce water activity, increase it again) cycle in the presence of a poly-ol might "push" the enzyme into a more active conformation.
Yes, the freeze drying increase enzyme activity, our group has found it in case of ligninolytic enzyme activity of some white rot fungi (Chander et al., 2014). The freeze drying process inturn reduces the water activity thus concentrating the enzyme hence an increase in activity is observed. I am attaching the paper for your reference.
Regards
Mukesh
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