N-Acetylneuraminic Acid Phosphatase (NANP)

Neu5Ac-9-phosphate phosphatase (Neu5Ac-9-Pase; EC 3.1.3.29) dephosphorylates Neu5Ac-9-phosphate to form N-acetylneuraminate (Neu5Ac), the main form of sialic acid in vertebrates that has important roles in protein-protein and cell-cell recognition.

Purified recombinant human HDHD4 catalyzed the dephosphorylation of Neu5Ac-9-phosphate with a catalytic efficiency more than 2 orders of magnitude higher than for any other substrate tested. The 248-amino acid human HDHD4 protein has 3 motifs found in phosphatases of the haloacid dehalogenase (HAD) family: the first with 2 extremely conserved aspartates, the second comprising a conserved serine or threonine, and the third comprising a conserved lysine and 2 conserved aspartates.