Effect of amoscanate derivative CGP 8065 on aminoacyl-tRNA synthetases in Ascaris suum

Evidence is provided for the occurrence of a multienzyme complex consisting of several aminoacyl-tRNA synthetases besides 'free enzymes' in Ascaris suum. The molecular mass of this complex was calculated to be about 10(6) daltons, compared to about 150 000 daltons for the seryl-tRNA synthetase. Leucyl-, isoleucyl-, arginyl- and lysyl-tRNA synthestases were found in the high molecular weight fraction. The Michaelis constants of these aminoacyl-tRNA synthetases were found to be in the range of 4 to 10 microM for amino acids and of 0.1 to 1.0 mM for ATP. Leucyl- and isoleucyl-tRNA synthetase interact with the amoscanate-derivative CGP 8065. The inhibition constants were determined to be 34 microM and 8 microM, respectively. The type of inhibition was found to be competitive with respect to ATP. It is proposed that the interference of CGP 8065 with the charging of tRNA might be another target for the chemotherapeutic attack of this amoscanate derivative.