The arginine pathway carbamoylphosphate synthase (CPSase A) from Saccharomyces cerevisiae was shown to be highly unstable and could not be substantially purified. In spite of this instability, a number of important properties of this enzyme were determined with crude preparations. A molecular weight of 140,000 (7.9S) was estimated for the native enzyme by sucrose gradient centrifugation; a significantly higher value, 175,000, was obtained by gel filtration on Sephadex. The enzyme is an aggregate consisting of two protein components, coded for by the unlinked genes cpaI and cpaII. These components were separated by diethylaminoethyl-cellulose chromatography. Their molecular weights, estimated by Sephadex gel filtration, were 36,000 and 130,000. The large component catalyzed the synthesis of carbamoylphosphate from ammonia. The small component was required in addition to the large one for the physiologically functional glutamine-dependent activity. Apparent Michaelis constants at pH 7.5 of 1.25 mM for glutamine and 75 mM for NH(4)Cl were measured with the native enzyme. The use of various glutamine analogs, including 2-amino-4-oxo-5-chloropentanoic acid, indicated that binding of glutamine to a site located on the small component was followed by transfer of its amide nitrogen to the ammonia site on the heavy component. This ammonia site was able to function independently of the utilization of glutamine. However, binding of glutamine was conjectured to cause a conformational change in the heavy component that greatly increased the rate of synthesis of carbamoylphosphate from ammonia. Glutamine, which was also shown to stabilize the aggregation of the two components, appeared to be a major effector of the catalytic and structural properties of CPSase A. In view of these observations, the CPSase A of yeast appears to share a number of structural and catalytic properties with the Escherichia coli enzyme. Obviously, the unlinked cpaI and cpaII genes of yeast are homologous to the adjacent carA and carB genes that code for the two subunits of the bacterial enzyme.
Increase the total number of rows showing on this page using the pull-down located below the table, or use the page scroll at the table's top right to browse through the table's pages; use the arrows to the right of a column header to sort by that column; filter the table using the "Filter" box at the top of the table.
| Gene/Complex | Qualifier | Gene Ontology Term | Annotation Extension | Evidence | Source | Assigned On |
|---|---|---|---|---|---|---|
| Carbamoyl-phosphate synthase arginine-specific | located in | cytoplasm | IDA | ComplexPortal | 2019-08-31 | |
| Carbamoyl-phosphate synthase arginine-specific | enables | ATP binding | IDA | ComplexPortal | 2019-08-31 | |
| Carbamoyl-phosphate synthase arginine-specific | involved in | L-arginine biosynthetic process | IDA | ComplexPortal | 2019-08-31 | |
| Carbamoyl-phosphate synthase arginine-specific | enables | carbamoyl-phosphate synthase (glutamine-hydrolyzing) activity | IDA | ComplexPortal | 2019-08-31 | |
| Carbamoyl-phosphate synthase arginine-specific | involved in | pyrimidine nucleotide biosynthetic process | IDA | ComplexPortal | 2019-08-31 | |
| CPA2 | part of | carbamoyl-phosphate synthase complex | IDA | SGD | 2013-08-07 | |
| CPA1 | part of | carbamoyl-phosphate synthase complex | IDA | SGD | 2013-08-07 |