Richard W. Carthew*, Johan A. Hellebust

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


The green alga Stichococcus bacillaris Naeg. is able to take up at least eleven amino acids. All of these except glutamic and aspartic acids are transported by carrier systems that obey saturation kinetics. The acidic amino acids enter the cell by passive diffusion. Michaelis‐Menten parameters (Ks and Vmax) were calculated for several amino acids. All obey simple Michaelis‐Menten behavior except for 2‐methylalanine and leucine which may have double carrier systems of different affinities. Interactions between pairs of amino acids suggest that there is at least one carrier system specific for basic amino acids and probably several systems specific for neutral amino acids. Further analysis of neutral amino acid interactions reveal that the uptake of several amino acids is incompletely inhibited by competitor uptake at infinite concentration. The simplest interpretation of the data is the operation of three carrier systems for neutral amino acids, one of which has higher affinity and broader specificity than the other two. The amino acid carrier systems appear to operate by an active mechanism. The metabolic poison DCCD inhibits uptake up to 99%. The capacities of the neutral amino acid carrier systems are increased when cells are grown in medium containing suboptimal concentrations of nitrogen.

Original languageEnglish (US)
Pages (from-to)441-446
Number of pages6
JournalJournal of Phycology
Issue number4
StatePublished - Jan 1 1982


  • Chlorophyta
  • Stichococcus bacillaris
  • amino acids
  • transport

ASJC Scopus subject areas

  • Aquatic Science
  • Plant Science

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