Biosynthesis of Arginine, Proline, and Related Compounds

Abstract

General aspects of arginine and proline metabolism in prokaryotes have been covered in various reviews. But studies with gram-positive bacteria are regrettably fragmentary. Streptomyces griseus and probably other species of Streptomyces catabolize arginine via 4-guanidinobutyramide and 4-guanidinobutyrate. It has been reported that Bacillus licheniformis possesses two P5C dehydrogenases, whose synthesis is controlled by arginine or proline. The cyclodeaminase reaction, which yields proline from ornithine in Clostridium species, seems to function primarily for ornithine catabolism rather than proline biosynthesis. The argCJBD-cpa-argF clusters from Bacillus subtilis and Bacillus stearothermophilus were first cloned in Escherichia coli by selecting for complementation of arginine auxotrophs. A significant finding was that where as mutations in ahrA, ahrB, or ahrD have no effect on levels of the biosynthetic enzymes, ahrC mutations lead to simultaneous loss of repressibility of the biosynthetic enzymes and of inducibility of the catabolic enzymes, with the implication that these two controls share at least one common component. Mutations to proline auxotrophy map at a further locus, proA; these mutants do not respond to arginine, possibly because in Streptomyces spp., levels of arginase are low and show only weak inducibility by arginine. Arginine, like many aminoacids, is a precursor of many of the secondary metabolites (including antibiotics) elaborated by Streptomyces spp. An intriguing connection between proline catabolism and transport and the production of a secondary metabolite, undecylprodigiosin, of which proline is a precursor, was found in Streptomyces coelicolor.