✦ LIBER ✦

Regulation and characterization of two inducible amino-acid transport systems inChlorella vulgaris

✍ Scribed by Norbert Sauer; Ewald Komor; Widmar Tanner

Publisher: Springer-Verlag
Year: 1983
Tongue: English
Weight: 705 KB
Volume: 159
Category: Article
ISSN: 0032-0935
DOI: 10.1007/bf00392075

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✦ Synopsis

Glucose or non-metabolizable glucose analogues induce two amino-acid transport systems in Chlorella vulgaris: an arginine system (arginine and lysine) and a proline system (proline, glycine, alanine and serine). The same amino-acid transport systems are induced in the absence of glucose, when the cells are depleted of their nitrogen source as judged by a comparison of K m values and the lack of additive induction by the two treatments. Changes in the concentration of neither internal free amino acids nor of soluble carbohydrate pools correlate perfectly with the induction of amino-acid transport. Also exogenous cAMP had no effect on the induction of transport. Both aminoacid transport systems are able to accumulate free amino acids more than 1000-fold. The accumulation plateau is not due to a steady state of influx and efflux, but rather arises by a shut-off of influx. No significant efflux is observed. The biological importance of this frequently observed behaviour in amino-acid transport is discussed.

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