Prolidase and prolinase activities in moderately and poorly differentiated lung adenocarcinoma

Prolidase (E.C.3.4.13.9) and prolinase (E.C.3.4.13.8) activities were determined in normal human lung and human lung adenocarcinomas of various degree of histologic differentiation. Since these dipeptidases were found to be enzymes catabolizing mainly collagen and simultaneously involved in the recycling of proline for collagen biosynthesis, the measurement of this protein and its degradation products in studied tissues (by hydroxyproline determination) was performed. It has been found that the activity of prolinase in G2-moderately and G3-poorly differentiated lung adenocarcinoma groups, was elevated compared to lung parenchyma and that the increase was proportional to the degree of adenocarcinoma differentiation. Prolidase activity was elevated only in G3 lung adenocarcinoma. The increase of prolidase and prolinase activities were accompanied by an increase of tissue collagen content. Collagen degradation products (CDP) represented one third of total collagen in control lung tissues while in lung adenocarcinomas the CDP represented significantly lower percentage of total tissue collagen. The results suggest that prolidase and prolinase activities may reflect: (i) degree of differentiation of lung adenocarcinoma and (ii) disturbances in tissue collagen metabolism.