Effect of long time storage on cytosolic glutathione S-transferases.

Glutathione S-transferases are a family of enzymes catalyzing the conjugation of glutathione to a wide variety of compounds. Stability of human liver cytosolic glutathione S-transferase enzyme activity and levels of glutathione S-transferase class Alpha and Mu were assessed. Cytosolic fractions of sixteen different patients were stored up to two years at three different temperatures: -20 degrees, -80 degrees and -196 degrees Celsius. Samples were assayed for glutathione S-transferase enzyme activity and glutathione S-transferase class Alpha and Mu levels, after 3, 6, 12 and 24 months of storage. No significant differences in glutathione S-transferase enzyme activity as well as in isoenzyme levels were found during this 24 months of storage at the three different temperatures. It is concluded that stability of glutathione S-transferases allows long term storage even at -20 degrees C, without significant loss of enzyme activity or enzyme protein.