Amino acid transport systems of JapaneseParamecium symbiont F36-ZK |
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Authors: | Yutaka Kato Nobutaka Imamura |
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Affiliation: | (1) Research Organization of Science and Engineering, Ritsumeikan University, Noji-Higashi 1-1-1, Kusatsu Shiga 525-8577, Japan;(2) Department of Pharmacy, College of Pharmaceutical Sciences, Ritsumeikan University, Noji-Higashi 1-1-1, Kusatsu Shiga 525-8577, Japan; |
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Abstract: | Analyses of amino acid transport systems in JapaneseParamecium symbiont F36-ZK were performed using14C-amino acids. Kinetic analyses of amino acid uptake and competitive experiments revealed three transport systems; a basic amino acid transport system, which catalyzed transport of L-Arg and L-Lys, a general amino acid transport system, which had broad specificity for 19 amino acids (but not L-Arg), and an alanine transport system. These three systems were considered to be capable of active transport. Amino acid-proton symport was indicated by the following data: decreases in pH of the medium observed during L-Ser and L-Ala uptake, and uptake of L-Arg, L-Ser and L-Ala being inhibited by carbonyl cyanide m-chlorophenylhydrazone, sodium azide and vanadate. The optimal pH for uptake of neutral amino acids and L-Arg was around 5 and 5 to 6.5, respectively. Uptake of L-Asp and L-Glu was very sensitive to pH and little uptake of L-Asp was measured above pH 6.0. Amino acid uptake was not inhibited by nitrate or ammonium, and cultured cells with ammonium also possessed constitutive uptake systems. |
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