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Sep 5, 2015
Nicotinamide adenine dinucleotide (NAD+) is a coenzyme for many NAD+-consuming proteins with diverse biological functions. Oscillations in NAD+ levels may influence several cellular signaling pathways. NAD+ synthesis via Preiss-Handler route (salvage reactions) has been extensively reported. However, the contribution of L-tryptophan/kynurenine catabolism in de novo NAD+ synthesis is poorly understood. Using L-[14C]-tryptophan tracing in four liver cancer cell lines and siRNA-mediated silencing of arylformamidase (AFMID), a key enzyme involved in L-tryptophan degradation, we demonstrate the contribution of L-tryptophan catabolism in de novo synthesis of NAD+ pools. NAD+ modulation is therefore important in maintaining cellular homeostasis and appropriate cellular functions according to nutrients availability.