HYDROLYSIS OF PROLINE DIPEPTIDES COMPLETELY FULFILLS THE PROLINE REQUIREMENT IN A PROLINE-AUXOTROPHIC CHINESE-HAMSTER OVARY CELL-LINE

Proline- and hydroxyproline-containing oligopeptides may be important in protein nutrition because intestinal hydrolases are incapable of recognizing their imido bonds. Peripheral tissues have a cytosolic enzyme prolidase that cleaves dipeptides containing C-terminal proline (X-Pro) or hydroxyproline. The role of dipeptides in intracellular metabolism is uncertain. This study examined the ability of X-Pro to provide proline to the proline-auxotrophic cell line, CHO-K1. The action of prolidase on exogenously supplied Gly-Pro, the most abundant dipeptide product of digestion, provided adequate proline to support normal cell growth of CHO-K1 cells in a dose-dependent manner. The growth curve generated by addition of Gly-Pro to CHO-K1 cells was similar to that due to proline. Two other structurally unrelated X-Pro also supported growth indistinguishably from Gly-Pro. Gly-Hyp was completely ineffective for growth. The ability of X-Pro to sustain cultures of a proline-auxotrophic cell line may be important in elucidating intracellular nutritional and physiological functions for those dipeptides.