The reported human NADsyn2 is ammonia-dependent NAD synthetase from a pseudomonad.
Nicotinamide-adenine dinucleotide (NAD+) synthetases catalyze the last step in NAD+ metabolism in the de novo, import, and salvage pathways that originate from tryptophan (or aspartic acid), nicotinic acid, and nicotinamide, respectively, and converge on nicotinic acid mononucleotide. NAD+ synthetase converts nicotinic acid adenine dinucleotide to NAD+ via an adenylylated intermediate. All of the known eukaryotic NAD+ synthetases are glutamine-dependent, hydrolyzing glutamine to glutamic acid to provide the attacking ammonia. In the prokaryotic world, some NAD+ synthetases are glutamine-dependent, whereas others can only use ammonia. Earlier, we noted a perfect correlation between presence of a domain related to nitrilase and glutamine dependence and then proved in the accompanying paper (Bieganowski, P., Pace, H. C., and Brenner, C. (2003) J. Biol. Chem. 278, 33049-33055) that the nitrilase-related domain is an essential, obligate intramolecular, thiol-dependent glutamine amidotransferase in the yeast NAD+ synthetase, Qns1. Independently, human NAD+ synthetase was cloned and shown to depend on Cys-175 for glutamine-dependent but not ammonia-dependent NAD+ synthetase activity. Additionally, it was claimed that a 275 amino acid open reading frame putatively amplified from human glioma cell line LN229 encodes a human ammonia-dependent NAD+ synthetase and this was speculated largely to mediate NAD+ synthesis in human muscle tissues. Here we establish that the so-called NADsyn2 is simply ammonia-dependent NAD+ synthetase from Pseudomonas, which is encoded on an operon with nicotinic acid phosphoribosyltransferase and, in some Pseudomonads, with nicotinamidase.
Bieganowski
Pawel
P
Structural Biology and Bioinformatics Program, Kimmel Cancer Center, Philadelphia, Pennsylvania 19107, USA.
Brenner
Charles
C
D019732:Amide Synthases / Q000737:chemistry* / Q000235:genetics*; D000641:Ammonia / Q000737:chemistry*; D001483:Base Sequence; D002892:Chromosomes, Human, Pair 22 / Q000378:metabolism; D003001:Cloning, Molecular; D018899:CpG Islands; D003545:Cysteine / Q000737:chemistry; D004247:DNA / Q000378:metabolism; D015723:Gene Library; D018698:Glutamic Acid / Q000737:chemistry; D005973:Glutamine / Q000737:chemistry; D006801:Humans; D006868:Hydrolysis; D008969:Molecular Sequence Data; D009132:Muscles / Q000378:metabolism; D009243:NAD / Q000737:chemistry*; D009535:Nicotinamidase / Q000378:metabolism; D016366:Open Reading Frames; D009876:Operon; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D011549:Pseudomonas / Q000378:metabolism*; D012689:Sequence Homology, Nucleic Acid
D005973:Glutamine; D009243:NAD; D018698:Glutamic Acid; D000641:Ammonia; D004247:DNA; D009535:Nicotinamidase; D019732:Amide Synthases; C038479:NAD+ synthase; D003545:Cysteine