N‐Acetylphenylalanyl‐tRNA Hydrolase from Yeast

This paper describes the purification and properties of an enzyme present in yeast which splits N-acetylphenylalanyl-tRNA to N-acetylphenylalanine and tRNA. The enzyme has been extensively purified, as shown by gel electrophoresis. The hydrolase has a molecular weight of 35000 as estimated by filtration on Sephadex G-150, is maximally active in the presence of a divalent cation (Mg2+, Mn2+ or Ca2+) and has a pH optimum at around neutrality. The enzyme is highly specific in hydrolyzing N-acetylphenylalanyl-tRNA (Km=0.4 μM). Phenylalanyl-tRNA is hydrolyzed with a similar apparent affinity but with an efficiency of 40% of that found for N-acetylphenylalanyl-tRNA. Other free or N-substituted aminoacyl-tRNAs are not substrates of this hydrolase. Neither of the two reaction products are effective inhibitors of this enzyme. Based on its substrate specificity, the trivial name of N-acetylphenylalanyl-tRNA hydrolase is proposed for this enzyme.