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Sphingolipid metabolism is tightly controlled by enzymes to regulate essential processes in human physiology. The central metabolite is ceramide, a pro‐apoptotic lipid catabolized by ceramidase enzymes to produce pro‐proliferative sphingosine‐1‐phosphate. Alkaline ceramidases are transmembrane enzymes that recently attracted attention for drug development in fatty liver diseases. However, due to their hydrophobic nature, no specific small molecule inhibitors have been reported. We present the discovery and mechanism of action of the first drug‐like inhibitors of alkaline ceramidase 3 (ACER3). In particular, we chemically engineered novel fluorescent ceramide substrates enabling screening of large compound libraries and characterized enzyme:inhibitor interactions using mass spectrometry and MD simulations. In addition to revealing a new paradigm for inhibition of lipid metabolising enzymes with non‐lipidic small molecules, our data lay the ground for targeting ACER3 in drug discovery efforts. [ABSTRACT FROM AUTHOR]

Abstract: Deciphering how an odorant activates an odorant receptor (OR) and how changes in specific OR residues affect its responsiveness are central to understanding our sense of smell. A joint approach combining site‐directed mutagenesis and functional assays with computational modeling has been used to explore the signaling mechanics of OR7D4. In this OR, a genetic polymorphism affects our perception of androstenone. Molecular simulations totaling 0.12 ms predicted that, similarly to observations for other G‐protein‐coupled receptors with known experimental structures, an activation pathway connects the ligand and the G‐protein binding site. The 3D model activation mechanism correlates with in vitro data and notably predicts that the OR7D4 WM variant is not activated. Upon activation, an OR‐specific sequence motif is the convergence point of the mechanism. Our study suggests that robust homology modeling can serve as a powerful tool to capture OR dynamics related to smell perception. [ABSTRACT FROM AUTHOR]