In Lactobacillus plantarum, carbamoyl phosphate is synthesized by two carbamoyl-phosphate synthetases (CPS): carbon dioxide differentiates the arginine-repressed from the pyrimidine-regulated CPS.
Carbamoyl phosphate (CP) is an intermediate in pyrimidine and arginine biosynthesis. Carbamoyl-phosphate synthetase (CPS) contains a small amidotransferase subunit (GLN) that hydrolyzes glutamine and transfers ammonia to the large synthetase subunit (SYN), where CP biosynthesis occurs in the presence of ATP and CO(2). Lactobacillus plantarum, a lactic acid bacterium, harbors a pyrimidine-inhibited CPS (CPS-P; Elagöz et al., Gene 182:37-43, 1996) and an arginine-repressed CPS (CPS-A). Sequencing has shown that CPS-A is encoded by carA (GLN) and carB (SYN). Transcriptional studies have demonstrated that carB is transcribed both monocistronically and in the carAB arginine-repressed operon. CP biosynthesis in L. plantarum was studied with three mutants (DeltaCPS-P, DeltaCPS-A, and double deletion). In the absence of both CPSs, auxotrophy for pyrimidines and arginine was observed. CPS-P produced enough CP for both pathways. In CO(2)-enriched air but not in ordinary air, CPS-A provided CP only for arginine biosynthesis. Therefore, the uracil sensitivity observed in prototrophic wild-type L. plantarum without CO(2) enrichment may be due to the low affinity of CPS-A for its substrate CO(2) or to regulation of the CP pool by the cellular CO(2)/bicarbonate level.
Nicoloff
H
H
Laboratoire de Microbiologie et de Génétique, Université Louis-Pasteur, CNRS UPRES A7010, Strasbourg, France.
Hubert
J C
JC
Bringel
F
F
D000595:Amino Acid Sequence; D001120:Arginine / Q000494:pharmacology; D001483:Base Sequence; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing) / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002221:Carbamyl Phosphate / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D007778:Lactobacillus / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D011743:Pyrimidines / Q000494:pharmacology; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic
D011743:Pyrimidines; D002245:Carbon Dioxide; D002221:Carbamyl Phosphate; D001120:Arginine; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing); C030986:pyrimidine