Phosphatase Subfamily PAPL
PAPL is found in holozoa but lost from most arthropods. Humans have a single member, PAPL (aka ACP7, PAPL1), but many invertebrates have multiple members, including 3 members each in Monosiga, Nematostella, sponge, and sea urchin. These appear to be independent expansions by protein sequence similarity, and in sea urchin, they form a tandem duplication cluster.
PAPL has a phosphatase domain and most members have an N-terminal signal peptide cleavage site. Though predicted to be secreted, human PAPL is found mostly in the cytoplasm (http://www.proteinatlas.org/ENSG00000183760-PAPL/tissue).
PAPL function is unclear. There may be some confusion in the literature, as PAPL/ACP7 may be confused with another PAP family member, ACP5, both of which are putative secreted proteins. The structural similarity between PAPL and ACP5 has been explored .