haloacid dehalogenase (HAD)-like 5'-nucleotidases similar to Saccharomyces cerevisiae Phm8p and Sdt1p
This family includes Saccharomyces cerevisiae Phm8p (phosphate metabolism protein 8) and Sdt1p (Suppressor of disruption of TFIIS). Phm8p participates in the ribose salvage pathway, it catalyzes the dephosphorylation of nucleotide monophosphates to nucleosides, its preferred substrates are nucleotide monophosphates AMP, GMP, CMP, and UMP. Phm8p is also a lysophosphatidic acid phosphatase, dephosphorylating lysophosphatidic acids (LPAs) to monoacylglycerol in response to phosphate starvation. Sdt1p is a pyrimidine and pyridine-specific 5'-nucleotidase; it is an NMN/NaMN 5'-nucleotidases involved in the production of nicotinamide riboside and nicotinic acid riboside, and is a pyrimidine 5'-nucleotidase with high specificity for UMP and CMP. 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.