title: Alpha-methyl-L-glutamic acid uptake by high affinity dicarboxylic amino acid transport system in Streptococcus faecalis.
abstract: The transport of alpha-methyl-L-glutamic acid was studied in Streptococcus faecalis. Energey-dependent uptake against substantial concentration gradients was observed. Kinetic experiments indicated that, in contrast to L-glutamic acid, only a single catalytic component (high affinity) and a diffusion controlled process participated in alpha-methyl-L-glutamic acid uptake. At concentrations up to 10 mM, alpha-methyl-glutamate transport was almost completely abolished in a mutant strain lacking a high affinity dicarboxylic amino acid transport system. In competition experiments, alpha-methylglutamic acid antagonized glutamate uptake via the high affinity system, and only slightly via the low affinity system. Column chromatography of cell extracts showed that very little (approx. 5%) of the accumulated amino acid was converted to metabolites during short term incubations. These studies indicate that, at concentrations up to 3-5 mM, alpha-methyl-L-glutamic acid can be used as a specific, relatively metabolically inert substrate of the high affinity dicarboxylic amino acid transport system in S. faecalis.
mesh_terms: D000600:Amino Acids, Dicarboxylic / Q000378:metabolism*; D001665:Binding Sites; D001692:Biological Transport; D001693:Biological Transport, Active; D004058:Diffusion; D013293:Enterococcus faecalis / Q000378:metabolism*; D005971:Glutamates / Q000378:metabolism*; D007700:Kinetics; D011485:Protein Binding; D013997:Time Factors
chemical_list: D000600:Amino Acids, Dicarboxylic; D005971:Glutamates