| Abstract: | Lysosomal H+-translocating ATPase (H+-ATPase) was solubilized with lysophosphatidylcholine and reconstituted into liposomes (Moriyama, Y., Takano, T. and Ohkuma, S. (1984) J. Biochem. (Tokyo) 96, 927-930). In this study, the sensitivities of membrane-bound, solubilized and liposome-incorporated ATPase to various anions and drugs were measured in comparison with those of similar forms of mitochondrial H+-ATPase (mitochondrial F0F1-ATPase) with the following results. (1) Bicarbonate and sulfite activated solubilized lysosomal H+-ATPase, but not the membrane-bound ATPase or ATPase incorporated into liposomes. All three forms of mitochondrial F0F1-ATPase were activated by these anions. (2) All three forms of both lysosomal H+-ATPase and mitochondrial F0F1-ATPase were strongly inhibited by SCN-, NO3- and F-, but scarcely affected by Cl-, Br- and SO2-4. (3) The solubilized lysosomal H+-ATPase was strongly inhibited by azide, quercetin, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl), 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS), 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) and oligomycin. Its sensitivity was almost the same as that of mitochondrial F0F1-ATPase. Neither membrane-bound ATPase nor ATPase incorporated into liposomes was affected appreciably by these drugs. These results indicate that the sensitivity to anions and drugs of lysosomal H+-ATPase depends on the form of the enzyme and that the sensitivity of the solubilized lysosomal H+-ATPase is very similar to that of mitochondrial F0F1-ATPase. On the other hand, the two ATPases differ in their sensitivity to N-ethylmaleimide and pyridoxal phosphate: only the mitochondrial ATPase is inhibited by pyridoxal phosphate whereas only the lysosomal ATPase is inhibited by N-ethylmaleimide. |
