Effect of Type of Carbohydrate on Amino Acid Accumulation and Utilization by Tetrahymena

Abstract

Both concentration and pattern of free amino acids in Tetrahymena pyriformis , as well as utilization, synthesis, and excretion of amino acids, were affected by type of carbohydrate in growth media. With glucose, cell pool concentrations were higher than with dextrin, and alanine and glycine together accounted for an average of 45% of the total pool. These two amino acids accumulated in similar proportions when their synthesis from essential amino acids was a prerequisite, as when they were provided by growth media, but they constituted only 15 to 18% of the free amino acids in cells from media with dextrin. Alanine, glycine, and glutamic acid were excreted into the medium regardless of whether they were provided by starting media; hence, they appear to be end products of the required metabolism of some of the essential amino acids. Both accumulation and excretion of the above non-essential amino acids were nearly twice as extensive in media providing glucose as the only carbohydrate as when the carbohydrate supplied was dextrin or dextrin plus glucose. Thus, the observed differences are not attributable to differences in osmolarity of monosaccharide and polysaccharide media. Free amino acid differences do not appear to be the immediate cause of the different growth-stimulating properties of such carbohydrates.