human N-acetylneuraminate-9-phosphate phosphatase, Escherichia coli house-cleaning phosphatase YjjG, and related phosphatases
N-acetylneuraminate-9- phosphatase (Neu5Ac-9-Pase; E.C. 3.1.3.29) catalyzes the dephosphorylation of N-acylneuraminate 9-phosphate during the synthesis of N-acetylneuraminate; Escherichia coli nucleotide phosphatase YjjG has a broad pyrimidine nucleotide activity spectrum and functions as an in vivo house-cleaning phosphatase for noncanonical pyrimidine nucleotides. This family belongs to the haloacid dehalogenase-like (HAD) hydrolases, a large superfamily of diverse enzymes that catalyze carbon or phosphoryl group transfer reactions on a range of substrates, using an active site aspartate in nucleophilic catalysis. Members of this superfamily include 2-L-haloalkanoic acid dehalogenase, azetidine hydrolase, phosphonoacetaldehyde hydrolase, phosphoserine phosphatase, phosphomannomutase, P-type ATPases and many others. HAD hydrolases are found in all three kingdoms of life, and most genomes are predicted to contain multiple HAD-like proteins. Members possess a highly conserved alpha/beta core domain, and many also possess a small cap domain, the fold and function of which is variable. HAD hydrolases are sometimes referred to as belonging to the DDDD superfamily of phosphohydrolases.
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