Arginyl- tRNA transferase activity as a maker of cellular aging in peripheral rat tissues

Abstract

Arginyl- tRNA transfers arginine from arginyl- t-RNA to the amino-terminus of acceptor proteins in the absence of ribosomes, and is considered to function in the modification of proteins at the post-translational level. Correlation of the enzyme activity and the arginine accepting capacity of endogenous proteins in relation to aging was studied. The distribution of arginyl- t-RNA transferase in peripheral rat tissues showed a high degree of tissue specificity. This was apparent not only in the quantitative measure of the enzyme, but also in the comparison of basal levels of activity to saturated substrate activities. Each tissue exhibited a characteristic response to exogenously applied acceptor protein. Significant age-dependent decreases in arginyl- t-RNA transferase activity were noted in rat kidney and liver preparations. These decreases were associated with a corresponding increase in unmodified endogenous acceptor proteins. No such alterations in enzyme activity or modification of endogenous acceptor proteins were observed in aging brain preparations. Brain, liver and kidney chromatin also exhibited characteristic age-associated alterations in arginine acceptor capacity which were unrelated to the changes in cytoplasmic arginyl- t-RNA transferase activity.