| Abstract: | A comparative study of the position specificity of tRNA-methylases from normal and tumour tissues was performed on yeast tRNA1Val as the substrates using partially purified enzyme preparations from rat kidney and carcinoma RA. As in the case of rat liver and Novikoff hepatoma, two methylated compounds are formed in yeast tRNA1Val under the action of rat kidney and carcinoma enzyme preparations: m5C is formed in the sequence C49--C52 located in the extra loop and A59 in the Tpsi-loop is is converted into m1A. The activity of m5C-methylase S-Ado-Met-tRNA-(cytosine-5)methyltransferase] (E. C. 2.1.1.29) is approximately equal in both tissues, whereas the activity of m1A-methylase S-Ado-Met-tRNA-(adenine-1)methyltransferase] (E. C. 2.1.1.36) in carcinoma is twice as high as in the kidney. The two enzymes do not differ in their position specificity. |
