Aspartic Acid Transport inMycobacterium smegmatis

ABSTRACT L ‐Aspartic acid was taken up by Mycobacterium smegmatis cells at a greater rate than D ‐aspartic acid. Kinetic studies of L ‐aspartic acid uptake revealed a curvilinear Lineweaver‐Burk plot. The observed kinetics could be accounted for by the existence of two different processes, a saturable and a nonsaturable. In contrast, the latter process was solely active for D ‐aspartic acid uptake. Competition studies indicated that aspartic acid and glutamic acid were similarly affected by the operation of 2 different processes. The existence of 2 similar catalytic transport processes, specific for dicarboxylic amino acids, was discussed.