title: Peptidase activity in Tetrahymena.
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.
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D003593:Cytoplasm / Q000201:enzymology; D004151:Dipeptides / Q000378:metabolism; D007700:Kinetics; D010447:Peptide Hydrolases / Q000378:metabolism*; D013379:Substrate Specificity; D013768:Tetrahymena / Q000201:enzymology*
chemical_list: D004151:Dipeptides; D010447:Peptide Hydrolases