proactivator polypeptide; saposin precursor; prosaposin (PSAP, GLBA)

Function

• lysosomal degradation of sphingolipids
• precursor of saposins
  • proteolytically processed to 4 small peptides (saposins), sphingolipid hydrolase activator peptides

Structure

• contains 2 saposin A-type domains
• contains 4 saposin B-type domains

Compartment

lysosome

Alternative splicing

named isoforms=3

Additional isoforms seem to exist

Pathology

• defects in PSAP saposin-A region are the cause of atypical Krabbe disease
• defects in PSAP saposin B region are a cause of metachromatic leukodystrophy variant
• defects in PSAP saposin C region are a cause of Gaucher disease variant
• defects in PSAP saposin D region are a cause of Tay-Sachs disease variant (GM2-gangliosidosis)
• defects in PSAP are the cause of combined saposin deficiency

More general terms

• glycoprotein
• protein precursor

Database

• UniProt: http://www.uniprot.org/uniprot/P07602.html
• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=5660
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:5660
• OMIM: https://mirror.omim.org/entry/176801
• OMIM: https://mirror.omim.org/entry/249900
• OMIM: https://mirror.omim.org/entry/610539
• OMIM: https://mirror.omim.org/entry/611721
• OMIM: https://mirror.omim.org/entry/611722