Purification and characterization of an aminoacyl-tRNA hydrolase from the filamentous fungus Fusarium culmorum

This paper describes the partial purification and characterization of an enzyme present in the fungus Fusarium culmorum which hydrolyzes aminoacyl-tRNA by splitting the ester linkage between the amino acid and the tRNA molecule. The enzyme has a molecular weight of 46 000 as estimated by gel filtration in Sephadex G-100, is maximally active in the presence of a divalent cation (Mg²⁺ or Mn²⁺) and has a pH maximum around neutrality. The enzyme is quite unspecific, hydrolyzing with practically the same efficiency aminoacyl-tRNAs with the amino group either free or substituted. The K_m of the enzyme for phenylalanyl-tRNA^Phe, and N-acetylphenylalanyl-tRNA is around 1 μM. Binding to the 80 S ribosomes but not to the 40 S ribosomal subunit renders the substrate resistant to the action of the hydrolase. The characteristics of this hydrolase are similar to those found for the aminoacyl-tRNA hydrolase of Artemia, and different from the more widely distributed peptidyl-tRNA hydrolases and other more specific aminoacyl-tRNA hydrolases found in different organisms.