Isoleucine and valine metabolism of Escherichia coli. XIV. Effect of thiaisoleucine.

Thiaisoleucine (2-amino-3-methylthiobutyrate) completely inhibited the growth of strain K-12 of Escherichia coli at a concentration of 5 x 10(-3)m. The inhibition was antagonized by growth-factor amounts of l-isoleucine. Thiaisoleucine inhibited the deamination of threonine and the transfer of (14)C-isoleucine to soluble ribonucleic acid and underwent transamination with alpha-ketoglutarate as the amino acceptor. In each case, the analogue appeared to be less effective than isoleucine as either an inhibitor or substrate.