Characterization of an Arabidopsis thaliana cDNA encoding an S-adenosylmethionine-sensitive threonine synthase Threonine synthase from higher plants

An Arabidopsis thaliana cDNA encoding an Sadenosylmethionine-sensitive threonine synthase (EC 4.2.99.2) has been isolated by functional complementation of an Escherichia coli mutant devoid of threonine synthase activity. Threonine synthase from A. thaliana was shown to be synthesized with a transit peptide. The recombinant protein is activated by Sadenosylmethionine in the same range as the plant threonine synthase and evidence is presented for an involvement of the N-terminal part of the mature enzyme in the sensitivity to Sadenosylmethionine.