Phosphorolysis of Aminoacyl‐tRNA by Polynucleotide Phosphorylase from Escherichia coli

Valyl‐transfer ribonucleic acid was degraded by polynucleotide phosphorylase from Escherichia coli in the presence of phosphate or arsenate. A compound that was identified as 2′(3′)‐O‐valyladenosine 5′‐pyrophosphate was isolated from the phosphorolytic digest of valyl‐tRNA while 2′(3′)‐O‐valyladenosine 5′‐monophosphate was isolated from the arsenolytic digest. It was concluded that valyl‐tRNA can be phosphorolyzed by polynucleotide phosphorylase. The rate of phosphorolysis of aminoacylated tRNA was lower than that of uncharged tRNA. N‐blocked derivatives of valyl‐tRNA and phenylalanyl‐tRNA were also phosphorolyzed by polynucleotide phosphorylase. Some possible uses of nucleoside diphosphates substituted in their sugar moiety are suggested.