Alteration of aminoacyl tRNA synthetases with age: accumulation of heat-labile enzyme molecules in rat liver, kidney and brain.

Age-related changes of aminoacyl tRNA synthetases were investigated in tissues from 3- to 24-month-old rats. The proportions of heat-labile enzymes in the liver, kidney and brain were 0-20% in young animals, but 15-40% in old animals. The proportions of heat-labile enzymes increase from about 15 months of age when the probability of death also increases greatly. These findings suggest that decrease in functional activities of various tissues in old animals is in some way related to the accumulation of these altered proteins.