Peptidase activity in Tetrahymena

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Abstract
This report strongly suggests that two compartments in Tetrahymena thermophila contain peptidase activity: the cytoplasm and the outer cell surface.Determinations of amino acid concentrations in the extracellular medium upon incubation of cells with peptides suggest that the surface‐bound peptidase activity hydrolyses di‐ and tri‐phenylalanine equally fast on a molar basis.Growth experiments designed to characterize the in vivo peptidase specificities showed that both T. thermophila and T. pyriformis can use L‐leucyl‐L‐leucine, but not L‐leucyl‐D‐leucine as a leucine donor. These results are independent of whether the cells form food vacuoles or not.