Introduction - NANP
The novel protein investigated by our group is N-acetylneuraminic acid (Neu5Ac) phosphatase, it was first release on Protein Data Bank
(PDB) on 18th April 2006, named 2gfh. Mus muscular (mouse) was used as the source of the gene and Escherichia coli was the
vector used to express the novel protein. In Homo sapiens (man), it was known to be as N-acetylneuraminate 9-phosphate (Neu5Ac-9-P)
phosphatase haloacid dehalogenase (HAD)-like hydrolase domain containing protein 4. Other aliases of the novel protein include C20orf147, NANP
and HDHD4. The gene encoding the protein was found to be on chromosome 20; location 20p11.1.
Neu5Ac-9-P phosphatase belongs to a large family of haloacid dehalogenase (HAD)-like hydrolases. The enzymes found within this classification
possess varied types of cleavage activities. Although many of its members are related by sequence cleave sites and reactions, many have evolved
to be used for specific biological functions within individual organisms.
These small molecule phosphatase enzymes have been found to exists in the various domains of life — Bacteria, Archaea, and Eucarya. The number
of genes found within each organism is varied from bacteria to eukaryotes. Bacterial Neu5Ac synthase and mammalian Neu5Ac-9-P synthase are
homologous proteins, sharing about 35% sequence identity1. Neu5Ac-9-P phosphatase dephosphorylates Neu5Ac-9-P to form Neu5Ac, the
main form of sialic acid.
Figure 1. Dephosphorylation of Neu5Ac-9-P is a reversible reaction with an end product of Neu5Ac (sialic acid) and a free phosphate.
Sialic acids are nine-carbon sugars with a carboxylate group that are found as components of many glycoproteins, glycolipids, and
polysaccharides in animals, viruses, and bacteria. The main form of sialic acid, Neu5Ac, is often present as the terminal sugar of N-
glycans on glycoproteins and glycolipids and plays an important role in protein–protein and cell–cell recognition 2; 3.
Figure 2. Chemical structure of sialic acid.(http://en.wikipedia.org/wiki/Sialic_acid)
Sialic acids are found widely distributed in animal tissues and in bacteria, especially in glycoproteins and gangliosides. The amino group
bears either an acetyl or a glycolyl group. Sialic acid consists of acetylated, sulfated, methylated, and lactylated derivatives and is a large
family of more than 50 members 4.