title: Cross-feeding of Escherichia coli mutants defective in the biosynthesis of nicotinamide adenine dinucleotide.
abstract: Mutants of Escherichia coli defective in the biosynthesis of nicotinamide adenine dinucleotide (NAD) are able to grow in a Casamino Acids medium lacking NAD and its immediate precursors, nicotinic acid and nicotinamide. This property has allowed the development of a system to measure cross-feeding between a nadA and a nadB mutant. This system provides a means of isolating the intermediate, prequinolinic acid, as well as a biological assay for the compound. The nadB mutant feeds the nadA mutant, indicating that the nadA enzyme occurs first in the pathway and the nadB enzyme second. No cross-feeding was detected between nadA and nadC or between nadB and nadC.
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D003470:Culture Media; D004792:Enzyme Precursors / Q000096:biosynthesis; D004926:Escherichia coli / Q000254:growth & development / Q000378:metabolism*; D009154:Mutation; D009243:NAD / Q000096:biosynthesis*; D009536:Niacinamide / Q000378:metabolism; D009539:Nicotinic Acids / Q000378:metabolism; D011725:Pyridines / Q000096:biosynthesis
chemical_list: D000596:Amino Acids; D003470:Culture Media; D004792:Enzyme Precursors; D009539:Nicotinic Acids; D011725:Pyridines; D009243:NAD; D009536:Niacinamide