Uptake of exogenous metabolites by virus-transformed cells: changes induced by temperature and pH.

Bestatin, (2S,3R)-3-amino-2-hydroxy-4-phenylbutanoyl]-(S)-leucine, inhibited aminopeptidase B and leucine aminopeptidase in a competitive manner and their K_i values were calculated to be 6 × 10^?8 and 2 × 10^?8M, respectively. Among all stereoisomers of bestatin synthesized, those which have a (2S)-configuration in the 3-amino-2-hydroxy-4-phenylbutanoyl moiety showed marked inhibition against aminopeptidase B and leucine aminopeptidase compared with the other isomers which have (2R)-configuration. One of the isomers, (2S,3S)-3-amino-2-hydroxy-4-phenylbutanoyl]-(R)-leucine, showed somewhat stronger activity against aminopeptidase B than bestatin. Aminopeptidase B appears to be a metallo-exopeptidase. It is proposed that bestatin and its active isomers are effective due to a mechanism other than a chelating action at the active center.