Abstract
Two types of intracellular aminopeptidase activity are present in E. coli B. One type, present in the 'soluble' fraction, is completely inactivated by chymotrypsin or trypsin; the other, in the particulate fractions ('ribosome' and 'membrane'), is resistant to these enzymes. The 'ribosomal' peptidase activity is present partially in a latent form which becomes activated on disruption of the ribosome structure. During the transition from log phase to post-log phase growth there is a progressive increase in the specific activity of the peptidase in the 'soluble' and 'membrane' fraction and a corresponding decrease in the 'ribosome' fraction.