Distributions of Post-Proline Cleaving Enzyme-, Converting Enzyme-, Trypsin- and Chymotrypsin-like Activities in Various Nephron Segments and in Brush-Border Membranes Isolated from Rat Kidney

Abstract

Distributions of post-proline cleaving enzyme-, converting enzyme-, chymotrypsin- and trypsin-like activities, were investigated in nephron segments and in brush-border membrane fraction isolated from rat kidney. These activities were found to be higher in the proximal tubule than in other segments, and were hardly detectable in the cortical collecting tubule. In the proximal tubule, trypsin-like activity showed the highest value in the pars convoluta, while the other peptidases showed their highest activities in the pars recta. Post-proline cleaving enzyme- and trypsin-like activities were also high in the glomerulus. In addition, post-proline cleaving enzymeand converting enzyme-like activities were found in the brush-border membrane, while chymotrypsin- and trypsin-like activities were found in the cell component (s) other than the brush-border membrane. From these distributions of the peptidases, it is speculated that peptides are degraded both in the glomerulus and in the proximal tubule, and that in the proximal tubule the peptides are degraded both in the brush-border membrane and in other cell component (s).