biostudies-literatureJain ANIAID NIH HHSNCI NIH HHSNIGMS NIH HHSeadq8331https://www.ebi.ac.uk/biostudies/studies/S-EPMC12832182biostudies-literatureUnknown387(6741)Breakdown of every transmembrane protein trafficked to lysosomes requires proteolysis of their hydrophobic helical transmembrane domains. Combining lysosomal proteomics with functional genomic datasets, we identified lysosomal leucine aminopeptidase (LyLAP; formerly phospholipase B domain-containing 1) as the hydrolase most tightly associated with elevated endocytosis. Untargeted metabolomics and biochemical reconstitution demonstrated that LyLAP is a processive monoaminopeptidase with preference for amino-terminal leucine. This activity was necessary and sufficient for the breakdown of hydrophobic transmembrane domains. LyLAP was up-regulated in pancreatic ductal adenocarcinoma (PDA), which relies on macropinocytosis for nutrient uptake. In PDA cells, LyLAP ablation led to the buildup of Science (New York, N.Y.)Leucine aminopeptidase LyLAP enables lysosomal degradation of membrane proteins.PMC12832182R35 GM149302R01 GM112948U54 AI170792R01 CA260249Olzmann JAGupta SZhang JDetomasi TCvon Linde TPerera RMDawson DWZoncu RCraik CSBommer GSpacci MJain ARohweder PLuo JCitron YRLange MAnderson DRademaker GHeremans IHernandez GAfalseLeucine aminopeptidase LyLAP enables lysosomal degradation of membrane proteins.Breakdown of every transmembrane protein trafficked to lysosomes requires proteolysis of their hydrophobic helical transmembrane domains. Combining lysosomal proteomics with functional genomic datasets, we identified lysosomal leucine aminopeptidase (LyLAP; formerly phospholipase B domain-containing 1) as the hydrolase most tightly associated with elevated endocytosis. Untargeted metabolomics and biochemical reconstitution demonstrated that LyLAP is a processive monoaminopeptidase with preference for amino-terminal leucine. This activity was necessary and sufficient for the breakdown of hydrophobic transmembrane domains. LyLAP was up-regulated in pancreatic ductal adenocarcinoma (PDA), which relies on macropinocytosis for nutrient uptake. In PDA cells, LyLAP ablation led to the buildup of 2025-01-01T00:00:00Z2025 Mar2026-07-15T06:07:37.72Z2026-07-01T03:07:43.812ZS-EPMC128321824014684610.1126/science.adq8331