Amino acid transport in Mycobacterium smegmatis.
The transport of d-alanine, d-glutamic acid, and d-valine in Mycobacterium smegmatis was compared quantitatively with that of their l-isomers. It appeared that the uptake of d-alanine was mediated by an active process displaying saturation kinetics characteristic of enzyme function, whereas the uptake of d-glutamic acid was accomplished by a passive process showing diffusion kinetics. Both processes were involved in the uptake of l-alanine, l-glutamic acid, d-valine, and l-valine. d-Valine competed with l-valine for entry into the cell through a single active process. d-Alanine and l-alanine also utilized the same active process, but the d-isomer could not enter the cell through the passive process. The passive process exhibited characteristics of diffusion, but was sensitive to sulfhydryl-blocking reagents and showed competition among structurally related amino acids. These last findings suggested that the passive process is a facilitated diffusion.
D000409:Alanine / Q000378:metabolism*; D002247:Carbon Isotopes; D002729:Chloromercuribenzoates / Q000494:pharmacology; D003470:Culture Media; D005971:Glutamates / Q000378:metabolism*; D007461:Iodoacetates / Q000494:pharmacology; D007700:Kinetics; D009161:Mycobacterium / Q000187:drug effects / Q000378:metabolism*; D013237:Stereoisomerism; D013696:Temperature; D014633:Valine / Q000378:metabolism*
D002247:Carbon Isotopes; D002729:Chloromercuribenzoates; D003470:Culture Media; D005971:Glutamates; D007461:Iodoacetates; D014633:Valine; D000409:Alanine