Active transport of D-alanine and related amino acids by whole cells of Bacillus subtilis.

Whole cells of Bacillus subtilis transported d-alanine and l-alanine by two different systems. The high-affinity system (K(m) of 1 muM and V(max) of 0.6 to 0.8 nmol/min per mg of protein) was specific for the two stereoisomers of alanine. The low-affinity system (K(m) of 10 muM for l-alanine and 20 muM for d-alanine and glycine) had a V(max) of 5 to 12 nmol/min per mg of protein. This system transported glycine, d-cycloserine, and d-serine, in addition to d- and l-alanine. Azide inhibited the uptake of these amino acids and caused the efflux of d-alanine from preloaded cells. These data suggest that transport of these amino acids is energized by the electron transport chain.