CYSTEINE UPTAKE FOR ACCUMULATION OF GLUTATHIONE BY THE CYANOBACTERIUMSYNECHOCYSTIS STRAIN PCC-6803

By incubation with precursor amino acids, L-glutanaate, L-cysteine, an d glycine, or with L-cysteine, the unicellular cyanobacterium Synechoc ystis strain PCC 6803 increased intracellular glutathione levels, unde r illumination with white light. L-Cystine could not serve as the prec ursor. Two transport systems for L-cysteine were evident in the stain: a high (K-s; L-cysteine concentration giving one-half of the maximum uptake, 21 similar to 35 mu M) and a low (K-s, 1.0 similar to 1.8 mM) affinity transport system, The latter, responsible for glutathione acc umulation, was an energy-requiring process, L-Cysteine uptake by the t wo transport systems. were Na+-independent, and inhibited by the prese nce of neutral amino acids and less inhibited by basic or acidic amino acids. These results suggested that the neutral amino acid symport(s) is involved in L-cysteine uptake for the GSH accumulation in this str ain.