molecular class B acid phosphatases, similar to Escherichia coli AphA
class B acid phosphatases (CBAPs) have been detected in a minority of bacterial species which include a number of major pathogens such as Escherichia coli, Haemophilus influenzae, and Streptococcus pyogenes. This family includes the CBAP Escherichia coli AphA. The purified enzyme is a broad-spectrum nucleotidase highly active against both 3'- and 5'-mononucleotides and monodeoxynucleotides, which can also act as a phosphotransferase. 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.