Endo, M., Minamikawa, T., Yamauchi, D. and Mitsuhashi, W. 1987. Nitrogen mobilization and peptidase activities in pods of maturing Phaseolus vulgaris fruits.—J. exp. Bot. 38: 1988-1995. Fresh weight of pods of maturing Phaseolus vulgaris fruits started to increase at 7 d after flowering (DAF) and reached a peak at 16-18 DAF. Seeds began to grow at 14 DAF and continued to increase in fresh weight during the developmental period examined (up to 27 DAF). After observations of fresh weight changes in pods and seeds, the developmental period of fruits was divided into five stages: I (0-7 DAF), II (8-12 DAF), III (13-16 DAF), IV (17-21 DAF) and V (22-27 DAF). Protein and free amino acid contents of pods of maturing fruits showed patterns consistent with the change in fresh weight of pods. In seeds, however, the protein content showed a marked increase in stages IV and V, but the amino acid content, which also increased in stage IV, reached a plateau in stage V. Endopeptidase (EPase) activity was found to increase throughout pod development and maturation, and is thought to play a leading role in the protein mobilization in pods. DEAE-cellulose chromatography of enzyme extracts from pods of stage V revealed three forms (a, b, c) of EPase. Experiments with inhibitors suggested that forms a and c are serine-class and sulphydryl enzymes, respectively. Aminopeptidase (APase) activities showed a gradual increase in stages II-IV and declined in stage V. Using polyacrylamide gel electrophoresis, each of alanine- and leucine-APases was shown to consist of at least five to six multiforms. Carboxypeptidase activity increased markedly between stages IV and V. This enzyme would seem to be more responsible for the pod protein mobilization in the final stage than APases.