The beta-amino acid transport system in Friedreich's ataxia.

Taurine and beta-alanine uptake in cultured skin fibroblasts proceeds through at least two distinct amino acid transport systems. The predominant beta amino acid uptake system which we refer to as the "Beta" system, incorporates taurine in a proportion of 95%. Beta-alanine in a proportion of 80% and does not incorporate beta-amino-isobutyric acid. A second transport system for beta-alanine seems to be operative cultured skin fibroblasts and this system shares the characteristics of system "L" for branched-chain and ring-side neutral amino acids. Results of ion depletion experiments, metabolic inhibition by drugs and blocking agents and previous kinetic studies of taurine and beta-alanine uptake in cultured skin fibroblasts failed to disclose any major difference in beta-amino acid transport between control individuals and patients with Friedreich's ataxia.