Rate of transacylation between 2' and 3'-O-L-phenylalanyladenosine

The 270-MHz proton NMR spectra of 2'-O-L-phenylalanyladenosine and 3'-O-L-phenylalanyladenosine in deuterated phosphate buffer were analyzed. The transacylation between these two isomers was studied by saturation transfer experiments on H1' proton resonances and the transacylation rate was directly determined to be 0.76 s-1 at pD 6.9 and 25 degrees C. This transacylation rate is appreciably slower than the rate of polypeptide chain elongation, suggesting the presence of enzymatic activity for the transacylation of aminoacyl-tRNA in protein biosynthesis.