Reassignment of the human aldehyde dehydrogenase ALDH8A1 (ALDH12) to the kynurenine pathway in tryptophan catabolismThe kynurenine pathway is the primary route for l-tryptophan degradation in mammals. Intermediates and side products of this pathway are involved in immune response and neurodegenerative diseases. This makes the study of enzymes, especially those from mammalian sources, of the kynurenine pathway worthwhile. Recent studies on a bacterial version of an enzyme of this pathway, 2-aminomuconate semialdehyde (2-AMS) dehydrogenase (AMSDH), have provided a detailed understanding of the catalytic mechanism and identified residues conserved for muconate semialdehyde recognition and activation.
Kinetics and structural features of dimeric glutamine-dependent bacterial NAD+ synthetases suggest evolutionary adaptation to available metabolitesNADH (NAD+) and its reduced form NADH serve as cofactors for a variety of oxidoreductases that participate in many metabolic pathways. NAD+ also is used as substrate by ADP-ribosyl transferases and by sirtuins. NAD+ biosynthesis is one of the most fundamental biochemical pathways in nature, and the ubiquitous NAD+ synthetase (NadE) catalyzes the final step in this biosynthetic route. Two different classes of NadE have been described to date: dimeric single-domain ammonium-dependent NadENH3 and octameric glutamine-dependent NadEGln, and the presence of multiple NadE isoforms is relatively common in prokaryotes.
Generation, Release, and Uptake of the NAD Precursor Nicotinic Acid Riboside by Human CellsBackground: Nicotinamide riboside (NR) and nicotinic acid riboside (NAR) can serve as precursors of NAD in human cells.Results: Human cells generate and release NR and NAR.Conclusion: NR and NAR are authentic intermediates of human NAD metabolism.Significance: Different cell populations might support each other's NAD pools by providing ribosides as NAD precursors.