Carbamate kinase from Pseudomonas aeruginosa: purification, characterization, physiological role, and regulation
| Autor: | O Nainan, A T Abdelal, W F Bibb |
|---|---|
| Rok vydání: | 1982 |
| Předmět: |
Carbamyl Phosphate
Arginine Microbiology chemistry.chemical_compound Adenosine Triphosphate Ammonia Anaerobiosis Molecular Biology Polyacrylamide gel electrophoresis Acetate kinase biology Futile cycle Phosphotransferases Carbamate kinase Hydrogen-Ion Concentration Phosphotransferases (Carboxyl Group Acceptor) Organophosphates Enzyme assay Adenosine Diphosphate Molecular Weight Kinetics Adenosine diphosphate Biochemistry chemistry Pseudomonas aeruginosa biology.protein Adenosine triphosphate Research Article |
| Zdroj: | Journal of Bacteriology. 151:1411-1419 |
| ISSN: | 1098-5530 0021-9193 |
| DOI: | 10.1128/jb.151.3.1411-1419.1982 |
| Popis: | Pseudomonas aeruginosa PAO1 possessed a carbamate kinase (CKase) distinct from carbamoylphosphate synthetase as well as from a constitutive acetate kinase which also catalyzes the phosphorylation of ADP by carbamoylphosphate. CKase was purified to homogeneity. Polyacrylamide gel electrophoresis of cross-linked CKase in the presence of sodium dodecyl sulfate showed that the enzyme consists of two subunits with identical molecular weights (37,000). The optimal pH of enzyme activity is 7.0. The double-reciprocal plot for carbamoylphosphate was linear at 2 mM ADP, yielding an apparent Km of 5 mM. However, at 0.25 mM ADP, the plot was concave upward, and a Hill plot of the data yielded a coefficient of 1.4. This apparent cooperativity at low ADP concentrations might serve to reduce the extent of catabolism of carbamoylphosphate under growth conditions yielding high energy charge. Experiments on the regulation of synthesis under various growth conditions showed a response to three regulatory signals: CKase was induced to high levels by anaerobiosis, induced to moderate levels by arginine, and repressed by ammonia. Thus, CKase expression is regulated in a manner that allows the enzyme to function as a provider of ammonia under aerobic conditions and of ATP under anaerobic conditions. ATP was an effective inhibitor of CKase activity; this inhibition provides the cell with an effective mechanism for avoiding a futile cycle resulting from the simultaneous operation of CKase and carbamoylphosphate synthetase when cells are grown in the presence of exogenous arginine. |
| Databáze: | OpenAIRE |
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