NAD Kinase (NADK) is an enzyme that belongs to the NAD Kinase family. It is a widely expressed enzyme, but it is not detected in skeletal muscle. NADK converts Nicotinamide Adenine Dinucleotide (NAD+) into NADP+, through phosphorylating the NAD+ coenzyme. NADP+ is an essential coenzyme in metabolism and provides reducing power to biosynthetic processes such as fatty acid biosynthesis. The structure of the NADK from the archaean Archaeoglobus fulgidus has been determined.