L-O-ETHYLTHREONINE - AN ANTAGONIST OF L-ISOLEUCINE

The metabolism of the new compound l-O-ethylthreonine by both mammalian and bacterial cells has been investigated and the results obtained showed that l-O-ethylthreonine was a metabolic antagonist of l-isoleucine. With a partially purified enzyme system from sarcoma 180 cells, the analogue was found to suppress the synthesis of l-isoleucyl-tRNA and the inhibition was competitively reversed by the natural amino acid. The mechanism of the inhibition appeared to be caused by the incorporation of the analogue into tRNA. In Escherichia coli B cells, l-O-ethylthreonine was found to be growth-inhibitory as well as to inhibit the incorporation of a number of amino acids into proteins. The analogue was incorporated into protein in bacterial cells although at a slower rate than that of l-isoleucine. © 1969.