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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 

Glutamine amidotransferase activity of NAD+ synthetase from Mycobacterium tuberculosis depends on an amino-terminal nitrilase domain.

NAD(+) synthetase (NadE; E.C. 6.3.5.1) from Mycobacterium tuberculosis utilizes both glutamine and ammonia to catalyze NAD(+) production, in contrast to the corresponding NH(3)-dependent enzymes from other prokaryotes. Here we report the site-directed mutagenesis of amino acids located in the N-terminal domain and predicted to be essential for glutamine hydrolysis. The residues forming the putative catalytic triad (Cys176, Glu52 and Lys121) were replaced by alanine; the mutated enzymes were expressed in the Escherichia coli Origami (DE3) strain and purified. The three mutants completely lost their glutamine-dependent activity, clearly indicating that Cys176, Glu52 and Lys121 are crucial for this activity. In contrast, the C176A and E52A variants, respectively, retained 90 and 30% of the original NH(3)-dependent specific activity, while the K121A mutant lost this activity. The results show that glutamine-amidotransferase activity is mediated by an N-terminal domain belonging to the superfamily of nitrilases. This domain, a new type of glutamine amide transfer ( GAT) domain, is the first to be characterized in bacterial NAD(+) synthetases.[1]

References

  1. Glutamine amidotransferase activity of NAD+ synthetase from Mycobacterium tuberculosis depends on an amino-terminal nitrilase domain. Bellinzoni, M., Buroni, S., Pasca, M.R., Guglierame, P., Arcesi, F., De Rossi, E., Riccardi, G. Res. Microbiol. (2005) [Pubmed]
 
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