DEPHOSPHORYLATION OF THE PHOSPHORYLATED ELONGATION FACTOR-II IN THE LIVERS OF CALORIE-RESTRICTED AND FREELY-FED RATS DURING AGING

Slowing down of the rate of protein synthesis during ageing is accompa nied by alterations in the amounts and activities of elongation factor s, eEF-1 and eEF-2. Since the activity of eEF-2 is regulated by phosph orylation, we have determined the changes in the activities of eEF-2-s pecific phosphorylating and dephosphorylating enzymes during ageing. P reviously, we have reported an age-related increase in the activity of eEF-2 kinase (BBRC, 192, 1210, 1993). We have now compared the activi ties of a dephosphorylating enzyme protein phosphatase 2A (PP2A) in yo ung and old liver extracts from freely-fed or calorie-restricted rats. The activity of PP2A remain unaltered during ageing. Furthermore, the re was no change in the kinetics and extent of PP2A-dependent and PP2A -independent dephosphorylation of eEF-2 during ageing.