Nicotinamide Riboside Kinase 1 (NRK1)

Nicotinamide adenine dinucleotide (NAD+) is essential for life in all organisms, both as a coenzyme for oxidoreductases and as a source of ADP-ribosyl groups used in various reactions. Nicotinic acid and nicotinamide, collectively known as niacin, are the vitamin precursors of NAD+. Nicotinamide riboside kinases, such as NRK1, function to synthesize NAD+ through nicotinamide mononucleotide using nicotinamide riboside as the precursor.Expression of NRK1 or NRK2 restored the ability of a yeast Nrk1 deletion strain to grow in the presence of nicotinamide riboside, indicating that NRK1 and NRK2 are authentic nicotinamide riboside kinases in vivo. They showed that NRK1 and NRK2 are highly specific for phosphorylation of nicotinamide riboside and the cancer drug tiazofurin, a nicotinamide riboside analog.