Uptake and metabolism of taurine in the green alga Chlorella fusca |
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Authors: | Susanne Biedlingmaier Ahlert Schmidt |
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Institution: | Botanisches Inst., Univ. München, Menzinger Str. 67, D-8000 München 19, FRG. |
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Abstract: | Taurine entered the alga Chlorella fusca Shihira et Krauss strain 21l-8b via a pH and energy-dependent system ("permease"). Transport followed triphasic kinetics from 10?6 to 10?2 M with Km values for taurine of 5.4 × 10?5, 4.1 × l0?4 and l.5 × 10?3 M. This uptake system was specific for sulfonic acids and showed no affinity for α- and β -amino acids or Na+; thus the permease of C. fusca is different from all known taurine transport systems with respect to structural specificity and lack of Na+ -dependence. Uptake was not observed in sulfate-grown algae but developed as a response to sulfate limitation within 2 h. Sulfate addition caused a rapid decline in taurine transport capacity. Labeled taurine was rapidly metabolized in C. fusca to sulfate and ethanolamine, suggesting oxidative hydrolysis as the mechanism of C-S bond cleavage. Further incorporation of these catabolic products in C - and S -metabolism was demonstrated. Taurine catabolism was also detected in other green algae and some cyanobacteria. |
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Keywords: | Cyanobacteria green algae sulfonate permease sulfur metabolism |
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