In enzymology, glucosamine-phosphate N-acetyltransferase (GNA) () is an enzyme that catalyzes the transfer of an acetyl group from acetyl-CoA to the primary amine in glucosamide-6-phosphate, generating a free CoA and N-acetyl-D-glucosamine-6-phosphate. This enzyme belongs to the family of transferases, a group of enzymes that transfers a very specific functional group, in this case acetyl, from a donor to a receptor. Specifically, this enzyme can be characterized as part of the acyltransferases family, since it involves the transfer of a general acyl group with a methyl as the substituent. Nomenclature The systematic name of this enzyme class is acetyl-CoA:D-glucosamine-6-phosphate N-acetyltransferase. Other names in common use include phosphoglucosamine transacetylase, phosphoglucosamine acetylase, glucosamine-6-phosphate acetylase, D-glucosamine-6-P N-acetyltransferase, aminodeoxyglucosephosphate acetyltransferase, glucosamine 6-phosphate acetylase, glucosamine 6-phosphate N-acetyltransferase, N-acetylglucosamine-6-phosphate synthase, phosphoglucosamine N-acetylase, glucosamine-phosphate N-acetyltransferase, and glucosamine-6-phosphate N-acetyltransferase. Function This enzyme is part of the hexosamine biosynthesis pathway (HBP), which is one of the glucose processing pathways in the general metabolism. This pathway shares the initial two steps with glycolysis and diverges only a small portion of glucose flux from this more traditional glycolytic pathway. Therefore, it is favored when there is negative feedback regulation on glycolysis, as in the case of large amounts of free fatty acids. The end product of this pathway is UDP-N-Acetylglucosamine, which is involved in the modification of complex molecules such as glycolipids, proteoglycans and glycoproteins. This end product acts as a carrier of N-Acetylglucosamine, which is the monomeric unit of chitin, a structural polymer that composes the shells of crustaceans and insects, as well as the cell wall of fungi. Furthermore, N-Acetylglucosamine is also a unit of the peptidoglycan polymer that composes the bacteria cell wall along with N-acetylmuramic disaccharide. More specifically, the GNA enzyme catalyzes the fourth step of the HBP pathway in eukaryotes, promoting a carbon transfer from Acetyl-CoA to the other substrate, D-Glucosamine-6-phosphate which will finally yield UDP-N-Acetylglucosamine. This is a small, but an important chemical step that is crucial to the properties of the sub-products of this metabolic pathway. The acetylation is carried out until the very end product of the hexamine pathway, and is very characteristic of the polymers formed with N-Acetylglucosamine. For instance, it constitutes one of the main difference in the molecular structure of chitin and cellulose, and explains many of the physical and chemical properties of these polymers. In the case of chitin, for example, computational studies have found that the acylation contributes to