Comparison of amino acid uptake and incorporation inTetrahymean pyriformis and hela cells

Abstract

1. Uptake of amino acids into the intracellular acid-soluble pool inTetrahymena pyriformis follows similar kinetics to those seen in mammalian cells. However, after an initial faster uptake phase, most amino acids show a more prolonged accumulation in the pool inTetrahymena, this second phase being inhibited by cycloheximide. Incorporation of amino acids into protein occurs with linear kinetics except in the case of glycine where it has an initial exponential phase lasting 3–4 min. These observations are in remarkably close agreement with the uptake of the same amino acids in mammalian cell cultures, including the slow start with glycine. 2. Experiments with the phenylalanine analogue,p-fluorophenylalanine, show that the acid-soluble pood inTetrahymena cannot be the obligate precursor supply for protein synthesis. Analysis of the fate of an existing acid-soluble pool confirms that it is not ‘discharged’ into protein in pulse-chase experiments. 3. These results, in conjunction with similar studies on other organisms reported in the literature, suggest that amino acid handling mechanisms could be similar in eukaryotic cells. The significance of the acid-soluble pool inTetrahymena, as in mammalian cells, is explicable in terms of the intracellular cyclic perfusion model of Wheatley and Inglis (1980).