Tissue distributions, substrate specificities and molecular sizes of human peptidases determined by separate gene loci

SUMMARY 1. The distribution of seven different peptidases thought to be determined by separate gene loci has been examined in a variety of human tissues. Although most of them are widely distributed, their relative activities vary from tissue to tissue. 2. The enzymes have been characterized in terms of their electrophoretie mobilities, their patterns of specificity with thirty‐five different substrates, and their molecular sizes as estimated by gel nitration. 3. One of the peptidases (peptidase S) which is not found in red cells but is present in most other tissues has not been previously described. It appears to hydrolyse a somewhat wider range of substrates than the other peptidases, and to have a larger molecular size (c. 245,000).