Lysosomal serine protease with tripeptidyl-peptidase I activity (PubMed:23587805). May act as a non-specific lysosomal peptidase which generates tripeptides from the breakdown products produced by lysosomal proteinases (By similarity). Requires substrates with an unsubstituted N-terminus (By similarity). Release of an N-terminal tripeptide from a polypeptide, but also has endopeptidase activity. Binds 1 Ca(2+) ion per subunit. Expressed in retina at 48 hours post-fertilization (at protein level). Detected in all retinal cell layers but has particularly strong expression in the outer nuclear layer and ganglion cell layer (at protein level). Activated by autocatalytic proteolytical processing. Morpholino knockdown of the protein in embryos results in developmental defects from 48 hours post-fertilization onwards, including reduced eye and head size, a curved body, small jaw, and loss of the swim bladder.