NAD+ is a cofactor for enzymes in mitochondrial energy production and glycolysis.

“several of these nad required enzymes are inside the mitochondria and this is another way nad participates in the generation of energy aside from itself being a type of energetic currency it also acts as a cofactor for enzymes involved in the production of energy from glucose outside of the mitochondria this is referred to as glycolysis many types of cells use like glycolysis as their primary source of energy for example red blood cells do not have any mitochondria so a hundred percent of the energy they require to perform their function of delivering oxygen and other goodies to other tissues in the body comes from glycolysis”