Pathway analysis of NAD+ metabolism

NAD+ plays a central role in cellular redox reactions and signaling. Prior research has shown that NAD+ is involved in DNA repair and aging processes. Established knowledge includes its role in redox balance and ADP-ribosylation reactions. However, the full range of biosynthetic and degradation pathways remains unclear. This gap motivated the use of EFMs to map all possible routes. No prior work had resolved the complete network of NAD+ metabolism. This study addresses that uncertainty by analyzing biosynthetic and degradation routes. The findings aim to clarify species-specific differences in NAD+ metabolism.

The aim of this study is to map all possible routes of NAD+ metabolism using elementary flux modes. The specific problem addressed is the incomplete understanding of NAD+ biosynthesis and degradation. The motivation stems from the need to clarify species-specific differences in metabolic networks. The study focuses on both biosynthetic and degradation pathways. It includes de novo synthesis and the Preiss-Handler pathway. The analysis covers NAD+ synthesis from various vitamin precursors. The goal is to identify all potential routes in the network. This contributes to understanding NAD+ metabolism in yeast and humans.

The study uses elementary flux modes to analyze NAD+ metabolism. It constructs a network of biosynthesis and degradation routes. The network includes all known biosynthetic pathways. De novo synthesis from tryptophan is included in the analysis. The Preiss-Handler pathway is also part of the network. NAD+ synthesis from other vitamin precursors is considered. The analysis identifies EFMs that degrade NAD+. It also detects futile cycles and other functional pathways.

The study identifies all potential routes in NAD+ metabolism. De novo synthesis from tryptophan is confirmed as an EFM. The Preiss-Handler pathway is detected as a valid route. NAD+ synthesis from other vitamin precursors is also identified. Several EFMs degrade NAD+ through ADP-ribosylation reactions. Some EFMs represent futile cycles with no net change. The analysis reveals significant differences between yeast and human networks. These differences include precursor use and biosynthetic routes.

The authors propose that EFMs provide a comprehensive view of NAD+ metabolism. They suggest that the network includes multiple biosynthetic and degradation routes. The findings indicate species-specific differences in precursor use. The study documents distinct biosynthetic routes in yeast and humans. The authors highlight the role of ADP-ribosylation in NAD+ degradation. They propose that futile cycles may have regulatory functions. The analysis supports the idea that NAD+ metabolism is complex and species-specific. These conclusions are based on the systematic analysis of EFMs.