A flavoprotein (FAD). L-Aspartate oxidase catalyses the first step in the de novo biosynthesis of NAD+ in some bacteria. O2 can be replaced by fumarate as electron acceptor, yielding succinate . The ability of the enzyme to use both O2 and fumarate in cofactor reoxidation enables it to function under both aerobic and anaerobic conditions . Iminosuccinate can either be hydrolysed to form oxaloacetate and NH3 or can be used by EC 18.104.22.168, quinolinate synthase, in the production of quinolinate. The enzyme is a member of the succinate dehydrogenase/fumarate-reductase family of enzymes .