METABOLISM OF AMINO ACIDS IN AGROBACTERIUM TUMEFACIENS: II. UPTAKE OFL-VALINE BY GROWING CELLS

Abstract

Growing cells of Agrobacterium tumefaciens strain IIBV7K (tumorogenic) metabolized14C-valine following its rapid uptake from the medium and released a non-amino metabolite (α-ketoisovaleric acid) into the extracellular fluid. This metabolite was taken up subsequently when the external valine concentration became limiting and was incorporated into protein, probably after conversion to an amino acid, α-Ketoisovaleric acid was not taken up when protein synthesis was blocked, e.g. by chloramphenicol, suggestive of an inducible entry system.α-Ketoisovaleric acid itself inhibited the uptake of14C-valine. It also suppressed the incorporation of label into protein by competition. Hydroxylamine inhibited the incorporation of14C-valine into protein without affecting valine entry into the cells. Glycine inhibited uptake as well as incorporation. Initially, glutamate inhibited14C-valine uptake and incorporation strongly; this was followed after 10 minutes, by rapid and linear entry and incorporation rates of the radioactive substrate.The results are discussed and compared with those from resting cells of A. tumefaciens, details of which were published in a previous paper.