Nicotinamide Riboside Phosphorylase (NRPh) is an enzyme that plays a vital role in the cellular metabolism of nicotinamide riboside (NR). NR is a form of vitamin B3 and functions as a precursor molecule for the synthesis of nicotinamide adenine dinucleotide (NAD+), a crucial coenzyme involved in various biological processes.
NRPh is responsible for the breakdown of NR into nicotinamide and ribose-5-phosphate, which are further utilized by specific metabolic pathways. This enzymatic reaction is known as phosphorolysis, involving the cleavage of a phosphoribosyl bond between NR and a phosphate group.
NRPh is predominantly found in the cytoplasm of cells, and its activity is regulated by various factors such as substrate availability, ATP levels, and feedback inhibition. It is highly specific for NR as its substrate, distinguishing it from other phosphorolytic enzymes.
The role of NRPh in cellular metabolism is crucial due to its involvement in the generation of NAD+, an essential molecule involved in various biological processes, including energy production, DNA repair, and cellular signaling. The breakdown of NR by NRPh provides a means to recycle and replenish the cellular pool of NAD+.
Overall, Nicotinamide Riboside Phosphorylase is an important enzyme in the metabolism of NR, as it catalyzes its breakdown into nicotinamide and ribose-5-phosphate, contributing to the regulation of NAD+ levels and thereby impacting various cellular functions.
