[Activity of valyl-tRNA-synthetase and alanyl-tRNA-synthetase in intact and denervated rabbit muscles].

The rate of acylation of non-fractionated tRNA from baker yeast and beef liver with valine-I-C14 and alanine-I-C14 had been measured. The yeast tRNA was found to be the active acceptor of valine while the beef tRNA intensively accepted alanine. The specific activities of valyl- and alanyl-tRNA synthetases from intact m. soleus (red) when measured with yeast tRNA were 4.3 and 3.3 times higher than the activities of the respective enzymes from intact m. gastrocnemius (mixed). 30 days after sciatic nerve section the activities of both aminoacyl-tRNA synthetases in denervated red and mixed muscles had become nearly equal. Equalization of aminoacyl-tRNA synthetases specific activities in the denervated muscles occured as a result of the changes in the catalytic properties and, possibly, in the intracellular concentration of the enzymes.