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Glutamine-dependent NAD+ synthetase. How a two-domain, three-substrate enzyme avoids waste.
| Content Provider | Semantic Scholar |
|---|---|
| Author | Wojcik, Marzena Seidle, Heather F. Bieganowski, Pawel Brenner, Charles |
| Copyright Year | 2006 |
| Abstract | Glutamine-dependent NAD(+) synthetase, Qns1, utilizes a glutamine aminotransferase domain to supply ammonia for amidation of nicotinic acid adenine dinucleotide (NaAD(+)) to NAD(+). Earlier characterization of Qns1 suggested that glutamine consumption exceeds NAD(+) production by 40%. To explore whether Qns1 is systematically wasteful or whether additional features account for this behavior, we performed a careful kinetic and molecular genetic analysis. In fact, Qns1 possesses remarkable properties to reduce waste. The glutaminase active site is stimulated by NaAD(+) more than 50-fold such that glutamine is not appreciably consumed in the absence of NaAD(+). Glutamine consumption exceeds NAD(+) production over the whole range of glutamine and NaAD(+) substrate concentrations with greatest efficiency occurring at saturation of both substrates. Kinetic data coupled with site-directed mutagenesis of amino acids in the predicted ammonia channel indicate that NaAD(+) stimulates the glutaminase active site in the k(cat) term by a synergistic mechanism that does not require ammonia utilization by the NaAD(+) substrate. Six distinct classes of Qns1 mutants that fall within the glutaminase domain and the synthetase domain selectively inhibit components of the coordinated reaction. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://brenner.lab.uiowa.edu/sites/brenner.lab.uiowa.edu/files/wysiwyg_uploads/wojcik06.pdf |
| Alternate Webpage(s) | http://biochem.uiowa.edu/brenner/documents/wojcik06.pdf |
| Alternate Webpage(s) | http://www.dartmouth.edu/~brenner/wojcik06.pdf |
| PubMed reference number | 16954203v1 |
| Volume Number | 281 |
| Issue Number | 44 |
| Journal | The Journal of biological chemistry |
| Language | English |
| Access Restriction | Open |
| Subject Keyword | Amino Acids Ammonia Class Dinucleoside Phosphates GLS gene Glutamine Kinetics Ligase Molecular Analysis Nicotinamide adenine dinucleotide (NAD) Transaminases mutant nicotinic acid adenine dinucleotide |
| Content Type | Text |
| Resource Type | Article |
