Mechanism of Spermine Stimulation of Rat‐Liver Isoleucyl‐tRNA Formation

The mechanism of spermine stimulation of rat-liver isoleucyl-tRNA formation has been studied by Cleland's method [Biochim. Biophys. Acta 67, 104–137 & 173–197 (1963)]. It was demonstrated that isoleucyl-tRNA formation proceeded through a ping-pong mechanism in the presence of spermine and magnesium. From a study of the effect of spermine on both the formation of isoleucyl-AMP · enzyme complex and on the subsequent formation of isoleucyl-tRNA from the isoleucyl-AMP · enzyme complex, evidence is presented that the stimulatory effect of spermine functions mainly through the spermine preventing the tRNA inhibition of isoleucyl-AMP · enzyme complex formation.