FIG. 10. Biosynthetic pathways for arginine, proline, polyamines. and associated intermediary metabolism, showing sites of gene action in biosynthesis and arginine catabolism (238. 241, 452, 569, 657, 696, 697, 1009, 1105, 1177, and references therein). Carbamyl phosphate for pyrimidine synthesis is made as a separate pool by a distinct enzyme (see pyr-3. Fig. 20). Interchange between the two pools occurs only in certain mutant combinations. ATP, Adenosine triphosphate.