The regulation of proline biosynthesis in maize roots

Proline or the proline analogues hydroxy-L-proline and azetidine-2-COOH inhibit the formation of proline from acetate-2- 14 C or glutamate-UL- 14 C in the 5-mm maize root tip. The inhibition of the incorporation of acetate-derived proline into protein is more severe than the inhibition of the total biosynthesis (soluble plus insoluble proline- 14 C). The results suggest that a portion of the proline biosynthesis, which becomes more prominent as the cells mature, is refractory to end product inhibition. The results also show that simultaneous additions of glucose promote the incorporation of proline-UL- 14 C into protein, exaggerate its accumulation as soluble proline, and reduce its oxidation.