Enzymes are the catalysts of the biochemical reactions that comprise metabolism; they do their job without changing themselves in the process. Enzymes are responsible for bringing about almost all of the chemical reactions in living organisms. Without enzymes, these reactions take place at a rate far too slow for the pace of metabolism.*
Enzymes being studied by researchers must be stored in a enzyme freezer at temperatures in the region of -10 to -25˚C (+14 to -13˚F). When stored at higher temperatures enzymes gradually denature and lose catalytic activity. Proper storage conditions are essential to ensure that the enzymatic activity on the label is indeed the activity inside the bottle. I have many not so fond memories of failed experiments in graduate school because the rather costly purified enzyme suspensions failed to perform as expected, all due to inadequate storage.
Household or commercial freezers are not satisfactory for enzyme storage because they lack critical temperature control and alarming features necessary to protect their contents. Specially designed enzyme freezers such as manufactured by Nor-Lake Scientific are available through Tovatech. They feature a microprocessor control with enlarged LED digital temperature displays accurate to within 1˚C. Temperatures in these laboratory freezers can be adjusted from -10 to -25˚C (+14 to -13˚F). A visual alarm activates when temperatures fall outside the setting.
An important specification point is that such freezers should be manually defrosted because automatic defrost can cause unacceptable temperature fluctuations within the unit. Contents should be quickly transferred to an alternate freezer when defrosting is scheduled.
Other desirable features include heavy duty spring loaded hinges, self-closing solid doors equipped with magnetic gaskets, and a cold-water evaporator to handle condensate. Top mounted compressors vent heat into the atmosphere and not to the base of the freezer.
*From the “Manual of Clinical Enzyme Measurements,” published by Worthington Biochemical Corporation.
How are enzymes stored in your laboratory? Do you have a written procedure for protecting them during defrosting operations?