The effect of erythritol on the stability of gamma-glutamyl transpeptidase and N-acetyl glucosaminidase in human urine.

In toxicology studies and clinical trials of erythritol, treated animals and human subjects had higher urine gamma-glutamyl transpeptidase [gamma-glutamyl transferase (gamma-GT)] than untreated controls. It has previously been reported that gamma-GT activity in frozen urine decreases with time; therefore, a study was undertaken to examine the effects of storage temperature, time, and the presence of erythritol on the stability of gamma-GT and N-acetyl glucosaminidase in human urine. In this study, it was found that the rate of decrease of the activity of gamma-GT is much greater at -20 degrees C than at -70 degrees C. Variation in the storage temperature of the frozen urine is particularly deleterious to gamma-GT. The addition of erythritol in a concentration of 5% reduces this decrease. Approximately 15% of N-acetyl glucosaminidase activity is lost in the initial process of freezing the urine. Thereafter, conditions of temperature, time, and the presence or absence of erythritol account for little additional loss of activity.