Identification of novel inhibitors of human SPCA2.

To identify specific inhibitors of the human secretary pathway Ca2+-ATPase 2 (hSPCA2), a recombinant hSPCA2 was expressed in Saccharomyces cerevisiae, and purified by Co2+-chelating chromatography. The isolated hSPCA2 catalyzed ATP hydrolysis in the presence of Ca2+ ions. The Ca2+ dissociation constant for ATPase activation was 25 nM. hSPCA2 activity was inhibited by thapsigargin, 2,2′-methylenebis(6-tert-butyl-p-cresol), and 4-octylphenol in the low-micromolar concentration range. Unexpectedly, the organic solvent wash from standard laboratory polypropylene microtubes showed strong inhibitory potency toward hSPCA2 activity. The extract was found to comprise mainly primary fatty acid amides (PFAAs) by NMR analysis. Individual PFAAs, especially oleamide and linoleamide, almost completely inhibited hSPCA2 activity with IC50 values of 7.5 μM and 3.8 μM, respectively.