Lysosomal serine protease with tripeptidyl-peptidase I activity (PubMed:11054422, PubMed:19038966, PubMed:19038967). May act as a non-specific lysosomal peptidase which generates tripeptides from the breakdown products produced by lysosomal proteinases (PubMed:11054422, PubMed:19038966, PubMed:19038967). Requires substrates with an unsubstituted N-terminus (PubMed:19038966). Release of an N-terminal tripeptide from a polypeptide, but also has endopeptidase activity. Binds 1 Ca(2+) ion per subunit. Inhibited by diisopropyl fluorophosphate (DFP). Monomer (PubMed:19038967). Interacts with CLN5 (PubMed:19941651). Interacts with CLN3 (PubMed:17237713). Identified by mass spectrometry in melanosome fractions from stage I to stage IV. Detected in all tissues examined with highest levels in heart and placenta and relatively similar levels in other tissues. Activated by autocatalytic proteolytical processing upon acidification (PubMed:11054422, PubMed:19038966, PubMed:19038967). N-glycosylation is required for processing and activity (PubMed:19038966, PubMed:19038967). The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Incorrectly indicated as originating from bovine. Neural Ceroid Lipofuscinoses mutation db Leiden Open Variation Database (LOVD)